Dose Of Measles-containing Vaccine Research Articles

Trends of Diphtheria–Tetanus–Pertussis and Measles Vaccine Coverage Preceding and during the COVID-19 Pandemic: An Analysis of the WHO European Region from 2000 to 2022

Available data highlights the significant impact of the COVID-19 pandemic on global vaccination trends. Despite this, comprehensive evaluations of these changes at the European level are still scarce. This study examines coverage for diphtheria, tetanus, and pertussis (DTP) and measles-containing vaccines (MCV) in the WHO European Region from 2000 to 2022. Vaccination coverage data, defined as the percentage of surviving infants who received the first and third doses of DTP (DTP1 and DTP3) and the first and second doses of MCV (MCV1 and MCV2), were extracted from UNICEF databases. Joinpoint regression analysis was employed to identify joinpoints in the time series and to estimate Annual Percent Changes (APCs) and Average Annual Percent Changes (AAPCs) over predefined timeframes. The coverages for DTP1 and MCV1 exhibit a similar trend, overall characterized by four joinpoints, one of which is in 2019. In contrast, the coverage for DTP3 does not show a significant temporal trend and lacks joinpoints, while the vaccination coverage for MCV2 shows a steadily increasing trend, with three identified joinpoints. A comparative analysis with the pre-pandemic period reveals a significant increase in the number of countries characterized by a decreasing trend during the pandemic period for all considered vaccination coverages, as indicated by the negative AAPC values. These results highlight the effect of the pandemic on childhood vaccination coverage. Compared to a mere descriptive analysis, the temporal analysis of trends using joinpoint regression provides significant opportunities to identify variations in vaccination coverages and pinpoint areas for intervention in future vaccination strategies.

Progress with the Second Dose Measles Vaccine Introduction and Coverage in the WHO African Region.

To achieve global and regional measles elimination objectives, the World Health Organization (WHO) recommends coverage of 95% or higher with two doses of measles-containing vaccine. A second dose of measles-containing vaccine (MCV) is typically administered in the second year of life after 12 months of age. We reviewed WHO-UNICEF estimates of national coverage (WUENIC) for the first and second doses of MCV (MCV1 and MCV2, respectively) and calculated drop-out rates between MCV1 and MCV2 for countries in the WHO African Region. From 2013 to 2023, estimated regional MCV2 coverage increased from 7% to 49%, and at the end of 2023, 43 (91%) countries had introduced MCV2 into their routine immunization programs. Countries with more antigens provided in the second year of life had higher mean and median MCV2 coverage levels, and lower drop-out rates between MCV1 and MCV2, as compared to countries providing only MCV2. Despite substantial progress, MCV2 coverage remains below the required levels to achieve and sustain elimination, and many countries have high drop-out rates between MCV1 and MCV2 coverage, indicating challenges in reaching children over 12 months of age. Increasing coverage of MCV2 and other vaccines in the second year of life is essential to achieving higher and equitable routine immunization coverage. This will require continued efforts to understand and mitigate barriers to reaching children after 12 months of age and accelerated implementation of available tools.

Impact of the COVID-19 Pandemic on Measles Vaccination Coverage and Estimated Catch-up Efforts for Serbia.

Measles is highly infectious, requiring ≥95% vaccine coverage rate (VCR) to prevent outbreaks. This study aimed to understand the impact of the COVID-19 pandemic on routine measles-containing vaccine (MCV) VCRs in Serbia and estimate national and regional catch-up vaccination required to prevent outbreaks. A multiplier model was used to calculate annual MCV dose 1 (MCV1) and MCV dose 2 (MCV2) VCRs for children 1-6 and 6-12 years of age, respectively, for 2011-2022. Postpandemic (2023-2024) VCRs were modeled. The numbers of administered doses were compared to prepandemic and postpandemic, and monthly catch-up rates were calculated for 12-, 18- and 24-month campaigns. Between prepandemic and pandemic periods, national MCV1 VCR decreased from 88% to 81%, while MCV2 VCR decreased from 92% to 89%, corresponding to 20,856 missed MCV1 and 8760 missed MCV2 doses. Assuming national VCRs returned to prepandemic levels post-2022, 18% of children 1-6 years of age and 11% of children 6-12 years of age would have missed their MCV1 and MCV2 doses, respectively, by 2024. To catch up missed doses under this scenario, most regions would require monthly catch-up rates of 25%, 16% or 12% for MCV1 and 14%, 9% or 7% for MCV2, considering 12-, 18- or 24-month campaigns, respectively. The pandemic negatively impacted MCV VCRs in Serbia, leaving a sizeable proportion of children with missed doses. Significant catch-up efforts are required to recover VCRs to prepandemic levels and avoid future measles outbreaks, with increased monthly administration rates versus those in prepandemic periods.

The Effects of Vaccination Status and Age on Clinical Characteristics and Severity of Measles Cases in the United States in the Post-Elimination Era, 2001-2022.

Despite high vaccine-effectiveness, wild-type measles can occur in previously vaccinated persons. We compared the clinical presentation and disease severity of measles by vaccination status and age in the post-elimination era in the United States. We included U.S. measles cases reported from 2001-2022. Breakthrough measles was defined as cases with ≥1 documented dose of measles-containing vaccine, classic measles as the presence of rash, fever, and ≥1 symptoms (cough, coryza, or conjunctivitis), and severe disease as the presence of pneumonia, encephalitis, hospitalization, or death. Vaccinated cases with low and high avidity IgG were classified as primary (PVF) and secondary (SVF) vaccine failures, respectively. Among 4,056 confirmed measles cases, 2,799 (69%) were unvaccinated, 475 (12%) were breakthrough infections, and 782 (19%) had unknown vaccination; 1,526 (38%), 1,174 (29%), and 1,355 (33%) were aged <5, 5-19, and ≥20 years, respectively. We observed a general decline in classic presentation and severe disease with an increase in the number of doses, and less complications among children aged 5-19 years compared to other age-groups. Among 93 breakthrough cases with avidity results, 11 (12%) and 76 (82%) were classified as PVF and SVF, respectively, with a higher proportion of PVFs having a classic measles presentation and severe disease than SVFs. Breakthrough measles cases tended to have milder disease with less complications. A small proportion of breakthrough infections were due to PVF than SVF. It is critical to maintain high MMR vaccination coverage in the United States to prevent serious measles illnesses.

Onward transmission of measles virus among vaccinated cases in a large community outbreak in Auckland, New Zealand, 2019

Background: Isolation of cases and quarantining of non-immune contacts are the mainstay of measles outbreak management in elimination settings. Serology testing of exposed contacts may not be feasible in large outbreaks; therefore, vaccination history is used as a proxy for determining immunity to measles and thus prevention of onward virus transmission. This study sought to investigate the risk of measles virus transmission from individuals with a history of one or two doses of measles-containing vaccine (MCV). Methods: Retrospective analysis of data from measles cases reported to Auckland Regional Public Health Service during the 2019 Auckland region measles outbreak. Vaccination history was verified using patient records and the New Zealand National Immunisation Register. Onward transmission was determined through case interviews and assessment of exposed contacts. Results: 1451 measles cases were assessed as eligible for vaccination at the time of measles outbreak. Of these, 1015 (70.0%) were unvaccinated, 220 (15.2%) had unknown vaccination status, 139 (9.6%) had received only one dose of MCV and 77 (5.3%) had received two doses of the vaccine. Compared to unvaccinated cases, the odds of onward transmission were lower among those with one dose only (OR 0.41, 95% CI: 0.20–0.75) or two doses of MCV (OR 0.44, 95% CI: 0.17–0.95). Median time since vaccination was longer among those with onward transmission compared to those without onward transmission for one and two doses of the vaccine, suggesting a potential effect of waning immunity among this cohort. Conclusion: These findings support the hypothesis that measles cases with a history of prior vaccination are less likely to transmit the virus to others compared to unvaccinated cases. Such information can be used to support decisions around quarantine requirements for vaccinated contacts in future measles outbreaks.

Using Regular High-Quality Serosurveys to Identify and Close National Immunity Gaps-Measles and Rubella Elimination in Japan.

In Japan, periodic measles outbreaks occurred mainly among young children under the routine immunization program with one dose of the measles-containing vaccine (MCV). A second dose of MCV was introduced in 2006. During a nationwide measles resurgence in 2007-2008, the most affected age group was teenagers. The national serological surveillance for vaccine-preventable diseases made it clear that there was a measles immunity gap among teenagers who had not received a second dose of MCV. To fill this immunity gap, nationwide non-selective supplementary immunization activities (SIAs) were carried out as a five-year program from April 2008 to March 2013 by providing an opportunity to be vaccinated with the measles and rubella vaccine during the first year of junior high school (12-13 years old) and the last year of high school (17-18 years old). The SIA was conducted with the strong involvement of local governments in charge of vaccination delivery and collaboration between the health and education sectors. Japan was verified as achieving measles elimination in 2015 and this has been sustained to date. The challenge of rubella elimination following a similar strategy of a serological diagnosis of an immunity gap and targeted vaccination is also discussed.

Mapping the Implementation Determinants of Second Dose Measles Vaccination in the World Health Organization African Region: A Rapid Review.

The second dose of measles-containing vaccines (MCV2) has significant programmatic relevance in the current immunisation landscape because it serves as both an opportunity to reduce measles immunity gaps and strengthen second year of life vaccination platforms. However, MCV2 coverage remains suboptimal across countries in the World Health Organization (WHO) African Region and this puts a significant number of children at risk of morbidity and mortality from measles despite the availability of an effective vaccine. There is an urgent need to strengthen the implementation of MCV2 but this requires a thorough and systematic understanding of contextual factors that influence it. The literature that describes the determinants of implementation of MCV2 in a manner that adequately accounts for the complexity of the implementation context is scarce. Therefore, the purpose of this rapid review was to explore the implementation determinants of MCV2 in the WHO African Region using systems thinking. Literature search in two databases (PubMed and Google Scholar) were conducted. After screening, a total of 17 eligible articles were included in the study. Thematic analysis of extracted data was performed to identify the implementation determinants, after which they were mapped using the Consolidated Framework for Implementation Research (CFIR). A causal loop diagram (CLD) was used to illustrate the linkages between identified determinants. We found 44 implementation determinants across the five CFIR domains, i.e., innovation, outer setting, inner setting, individual, and implementation process. The majority of identified determinants are within the individual domain followed by the inner setting domain. The CLD showed that multiple contingent connections and feedback relationships exist between the identified implementation determinants within and across CFIR domains. The linkages between the implementation determinants revealed three balancing and reinforcing loops each. The findings suggest that implementation determinants of second-dose measles vaccination in the WHO African Region are complex, with multiple interconnections and interdependencies, and this insight should guide subsequent policies. There is an urgent need for further implementation research with embedded CLD in specific settings to inform the design of tailored systemic strategies to improve the implementation effectiveness of MCV2.

Measles outbreak in 2019: a warning for the post-COVID-19 pandemic period.

Introduction. At the end of 2019 and the year before, there was a significant spread of measles in the World Health Organization (WHO) European Region.Gap statement. Among the countries that reported, a measles outbreak was Bosnia and Herzegovina (BiH).Aim. To describe the measles outbreak in BiH (an entity of the Federation of BiH, FBiH) in 2019.Methodology. Confirmatory IgM serology, measles nucleic acid detection by real-time RT-PCR and virus genotyping were done in the WHO-accredited laboratory for measles and rubella at the Clinical Center of the University of Sarajevo, Unit for Clinical Microbiology. Genotype was determined in all measles-RNA-positive cases by sequence analysis of the 450 nt fragment coding the C-terminal of measles virus nucleoprotein (N).Results. From 1 January to 31 December 2019, 1332 measles cases were reported, with the peak observed in April 2019 (413/1332, 31.01 %). Sarajevo Canton had the highest incidence, number of cases and percentage (206.4; 868/1332; 65.17 %) of measles cases. Around four-fifths of infected persons were unvaccinated (1086/1332, 81.53 %), while 4.58 % of the patients (61/1332) were immunized with one dose of measles-containing vaccine. The highest proportion of cases was found in children 0-6 years of age (738/1332, 55.41 %). Measles IgM positivity was determined in 75.88 % (346/456), while virus RNA was detected in 82.46 % (47/57) of the swab samples. All measles virus sequences belonged to genotype B3. SNP (position 216: C=>T) was detected in 1 of the 40 sequences obtained during this outbreak.Conclusion. Due to suboptimal immunization coverage, BiH belongs to countries at a high risk for measles outbreaks. Post-COVID-19 (coronavirus disease 2019) pandemic, targeted and tailored strategies are required to ensure routine vaccination demand and acceptance and broad partner and stakeholder group participation.

Qualitative Insights on Barriers to Receiving a Second Dose of Measles-Containing Vaccine (MCV2), Oromia Region of Ethiopia.

Introduction: Ethiopia introduced a second dose of measles-containing vaccine (MCV2) in 2019 to provide further protection against measles and further progress toward elimination. However, the sub-optimal coverage of both MCV1 and MCV2 suggest challenges with vaccine uptake. In this qualitative study, we explored barriers to the uptake of MCV2 among caregivers, community leaders, and healthcare workers (HCWs). Method: A qualitative study was conducted between mid-April and mid-May 2021. We selected ten woredas (districts) in the Oromia Region, Ethiopia, stratified by settlement type (urban/rural), MCV1 coverage (high ≥ 80%; low < 80%), and history of measles outbreaks between June 2019 and June 2020. Experiences surrounding barriers to MCV2 uptake were discussed via focus group discussions (FGDs) and in-depth interviews (IDIs) with caregivers of children 12-23 and 24-36 months and key informant interviews (KIIs) with HCWs who administer vaccines and with community leaders. Participants were recruited via snowball sampling. Recorded data were transcribed, translated to English, and analyzed using ATLAS.ti v.09. Results: Forty FGDs and 60 IDIs with caregivers, 60 IDIs with HCWs, and 30 KIIs with community leaders were conducted. Barriers among caregivers included lack of knowledge and awareness about MCV2 and the vaccination schedule, competing priorities, long wait times at health facilities, vaccine unavailability, negative interactions with HCWs, and transportation challenges. At the community level, trusted leaders felt they lacked adequate knowledge about MCV2 to address caretakers' questions and community misconceptions. HCWs felt additional training on MCV2 would prepare them to better respond to caretakers' concerns. Health system barriers identified included the lack of human, material, and financial resources to deliver vaccines and provide immunization outreach services, which caretakers reported as their preferred way of accessing immunization. Conclusions: Barriers to MCV2 uptake occur at multiple levels of immunization service delivery. Strategies to address these barriers include tools to help caretakers track appointments, enhanced community engagement, HCW training to improve provider-client interactions and MCV2 knowledge, and efforts to manage HCW workload.

Second dose of measles-containing vaccine coverage and associated factors among children aged 24-36 months in Gondar city, Central Gondar, Northwest Ethiopia, 2023.

Measles caused 207,000 deaths worldwide in 2019. Ethiopia ranks among the top 10 countries in the world with the highest number of measles cases. However, the coverage of the second dose of measles-containing vaccine (MCV2) remains low. To increase coverage, the government of Ethiopia launched a nationwide measles vaccination campaign. Despite this intervention, the coverage is still below target, and there is scarce information in the study area. Therefore, this study aimed to assess MCV2 coverage and associated factors among children aged 24-36 months in Gondar city, Central Gondar, Northwest Ethiopia, 2023. A community-based cross-sectional study was conducted among 621 children aged 24-36 months using a systematic random sampling technique from 25 April to 25 May. A pre-tested, interviewer-administered, and structured questionnaire was used and collected using Kobo Toolbox and then transferred to Stata version 17 for further analysis. The binary logistic regression model was used to identify factors, and the presence of an association was declared using a p-value of <0.05. Similarly, an adjusted odds ratio with a 95% confidence interval was used to interpret the direction and strength of an association. A total of 621 children, with a response rate of 98.1%, participated in the study. The coverage of the second dose of MCV was 75.68% (95% CI: 72.1-78.9). The following factors were significantly associated with measles-containing vaccine second dose (MCV2) coverage: father as the household head (AOR: 3.06, 95% CI: 1.43-6.44), first birth order (AOR: 4.45, 95% CI: 1.21-16.3), four and above antenatal care (ANC) follow-ups (AOR: 5.18, 95% CI:1.62-16.5), postnatal care (PNC) service utilization (AOR: 2.57, 95% CI:1.27-5.15), at least two doses of vitamin A uptake (AOR: 6.39, 95% CI: 2.67-15.2), mothers having high awareness (AOR: 1.97, 95% CI:1.15-3.4), and good perception (AOR: 3.6, 95% CI: 2-6.47) about measles vaccination. The coverage of MCV2 in the study area is lower than the national and global target of above 95%. Head of household, birth order, ANC follow-up, PNC service utilization, vitamin A uptake, awareness, and perception of mothers about measles vaccination were significant factors for MCV2 coverage. Creating awareness, increasing the perception of mothers about measles vaccination, and strengthening the ANC and PNC services will increase the coverage.

Measles Vaccine Coverage and Disease Outbreaks: A Systematic Review of the Early Impact of COVID-19 in Low and Lower-Middle Income Countries.

Objectives: We aimed to evaluate changes to measles-containing vaccine (MCV) provision and subsequent measles disease cases in low- and lower-middle income countries (LICs, LMICs) in relation to the COVID-19 pandemic. Methods: A systematic search was conducted of MEDLINE, OVID EMBASE and PubMed records. Primary quantitative and qualitative research studies published from January 2020 were included if they reported on COVID-19 impact on MCV provision and/or measles outbreak rates within LICs and LMICs. Results: 45 studies were included. The change in MCV1 vaccination coverage in national and international regions ranged -13% to +44.4% from pre-COVID time periods. In local regions, the median MCV1 and overall EPI rate changed by -23.3% and -28.5% respectively. Median MCV2 rate was disproportionally impacted in local areas during COVID-interruption time-periods (-48.2%) with ongoing disruption in early-recovery time-periods (-17.7%). 8.9% of studies reported on vaccination status of confirmed measles cases; from these, 71%-91% had received no MCV dose. Conclusion: MCV vaccination coverage experienced ongoing disruption during the recovery periods after initial COVID-19 disruption. Vaccination in local area datasets notably experienced longer-term disruption compared to nationally reported figures.

Recovery of measles-containing and HPV vaccine ordering post-COVID-19 pandemic: Trends by public vs. private funding source, urbanicity, and state – United States, January 2018 – December 2022

ObjectiveTo assess recovery in childhood and adolescent vaccine ordering since initial declines in 2020 due to COVID-19 pandemic-related disruptions. MethodsUsing vaccine ordering data provided by Merck & Co., Inc., Rahway, NJ, USA, the number of measles-containing vaccine doses ordered each month in the U.S. during January 1, 2020-May 31, 2022 were compared to doses ordered during the corresponding month in 2018 and human papillomavirus (HPV) vaccine doses ordered during January 1, 2020-December 31, 2022 were compared to corresponding month in 2019. Differences stratified by public vs. private funding source and state and urbanicity of the county where the provider is located were examined. ResultsThe cumulative deficit for measles-containing vaccines was 1,314,179 doses (-5.7%) as of May 2022 and 3,911,020 doses (-13.6%) for HPV vaccine as of December 2022. Deficits in publicly funded doses and HPV doses ordered in rural counties were greater than deficits in privately funded doses and HPV doses ordered in urban counties. ConclusionsFindings show that monthly measles-containing and HPV vaccine ordering has recovered; however, deficits remain. Greater deficits in publicly funded vaccine doses and HPV ordering in rural counties suggest varying level of recovery. To reduce gaps in deficits, health care providers are strongly encouraged to use every visit to recommend needed vaccines.

Immunisation coverage and factors associated with incomplete immunisation in children under two during the COVID-19 pandemic in Sierra Leone

BackgroundRoutine childhood immunisation is one of the most important life-saving public health interventions. However, many children still have inadequate access to these vaccines and millions remain (partially) unvaccinated globally. As the COVID-19 pandemic disrupted health systems worldwide, its effects on immunisation have become apparent. This study aimed to estimate routine immunisation coverage among children under two in Sierra Leone and to identify factors associated with incomplete immunisation during the COVID-19 pandemic.MethodsA cross-sectional household survey was conducted in three districts in Sierra Leone: Bombali, Tonkolili and Port Loko. A three-stage cluster sampling method was followed to enrol children aged 10–23 months. Information regarding immunisation status was based on vaccination cards or caretaker’s recall. Using WHO’s definition, a fully immunised child received one BCG dose, three oral polio vaccine doses, three pentavalent vaccine doses and one measles-containing vaccine dose. Following the national schedule, full immunisation status can be achieved at 9 months of age. Data were weighted to reflect the survey’s sampling design. Associations between incomplete immunisation and sociodemographic characteristics were assessed through multivariable logistic regression.ResultsA total of 720 children were enrolled between November and December 2021. Full vaccination coverage was estimated at 65.8% (95% CI 60.3%-71.0%). Coverage estimates were highest for vaccines administered at birth and decreased with doses administered subsequently. Adjusting for age, the lowest estimated coverage was 40.7% (95% CI 34.5%-47.2%) for the second dose of the measles-containing vaccine. Factors found to be associated with incomplete immunisation status were: living in Port Loko district (aOR = 3.47, 95% CI = 2.00-6.06; p-value < 0.001), the interviewed caretaker being Muslim (aOR = 1.94, 95% CI = 1.25–3.02; p-value = 0.015) and the interviewed caretaker being male (aOR = 1.93, 95% CI = 1.03–3.59, p-value = 0.039).ConclusionThough full immunisation coverage at district level improved compared with pre-pandemic district estimates from 2019, around one in three surveyed children had missed at least one basic routine vaccination and over half of eligible children had not received the recommended two doses of a measles-containing vaccine. These findings highlight the need to strengthen health systems to improve vaccination uptake in Sierra Leone, and to further explore barriers that may jeopardise equitable access to these life-saving interventions.

The decline of measles antibody titers in previously vaccinated adults: a cross-sectional analysis.

The global reemergence of measles in 2018-2019 reinforces the relevance of high-coverage immunization to maintain the disease elimination. During an outbreak in the Sao Paulo State in 2019, several measles cases were reported in individuals who were adequately vaccinated according to the current immunization schedule recommends. This study aimed to assess measles IgG antibody seropositivity and titers in previously vaccinated adults. A cross-sectional study was conducted at CRIE-HC-FMUSP (Sao Paulo, Brazil) in 2019. It included healthy adults who had received two or more Measles-Mumps-Rubella vaccines (MMR) and excluded individuals with immunocompromising conditions. Measles IgG antibodies were measured and compared by ELISA (Euroimmun®) and chemiluminescence (LIASON®). The association of seropositivity and titers with variables of interest (age, sex, profession, previous measles, number of measles-containing vaccine doses, interval between MMR doses, and time elapsed since the last MMR dose) was analyzed. A total of 162 participants were evaluated, predominantly young (median age 30 years), women (69.8%) and healthcare professionals (61.7%). The median interval between MMR doses was 13.2 years, and the median time since the last dose was 10.4 years. The seropositivity rate was 32.7% by ELISA and 75.3% by CLIA, and a strong positive correlation was found between the tests. Multivariate analyses revealed that age and time since the last dose were independently associated with positivity. Despite being a single-center evaluation, our results suggest that measles seropositivity may be lower than expected in adequately immunized adults. Seropositivity was higher among older individuals and those with a shorter time since the last MMR vaccine dose.

Trends of measles in Tanzania: A 5-year review of case-based surveillance data, 2018-2022

ObjectivesTanzania observed a gradual increase in the number of measles cases since 2019 with a large outbreak recorded during 2022. This study describes the trend of measles in Tanzania over a 5-year period from 2018-2022. MethodsThis was a descriptive study conducted using routine measles case-based surveillance system including 195 councils of the United Republic of Tanzania. ResultsBetween 2018 and 2022 there were 12,253 measles cases reported. Out of 10,691 (87.25%) samples tested by enzyme-linked immunosorbent assay, 903 (8.4%) were measles immunoglobulin M positive. The highest number of laboratory-confirmed measles cases was in 2022 (64.8%), followed by 2020 (13.8%), and 2019 (13.5%). Out of 1279 unvaccinated cases, 213 (16.7%) were laboratory-confirmed measles cases compared to 77/723 (10.6%) who were partially vaccinated and 71/1121 (6.3%) who were fully vaccinated (P < 0.001). Children aged between 1-4 years constituted the most confirmed measles cases after laboratory testing, followed by those aged 5-9 years. There was a notable increase in the number of laboratory-confirmed measles cases in children <1 year and 10-14 years during 2022 compared to previous years. The vaccination coverage of the first dose of measles-containing vaccine (MCV1) was maintained >90% since 2013 while MCV2 increased gradually reaching 88% in 2022. ConclusionsAccumulation of susceptible children to measles due to suboptimal measles vaccination coverage over the years has resulted in an increase in the number of laboratory-confirmed measles cases in Tanzania with more cases recorded during the COVID-19 pandemic. Strengthening surveillance, routine immunization, and targeted strategies are key to achieving the immunity levels required to interrupt measles outbreaks.

Geospatial Analyses of Recent Household Surveys to Assess Changes in the Distribution of Zero-Dose Children and Their Associated Factors before and during the COVID-19 Pandemic in Nigeria.

The persistence of geographic inequities in vaccination coverage often evidences the presence of zero-dose and missed communities and their vulnerabilities to vaccine-preventable diseases. These inequities were exacerbated in many places during the coronavirus disease 2019 (COVID-19) pandemic, due to severe disruptions to vaccination services. Understanding changes in zero-dose prevalence and its associated risk factors in the context of the COVID-19 pandemic is, therefore, critical to designing effective strategies to reach vulnerable populations. Using data from nationally representative household surveys conducted before the COVID-19 pandemic, in 2018, and during the pandemic, in 2021, in Nigeria, we fitted Bayesian geostatistical models to map the distribution of three vaccination coverage indicators: receipt of the first dose of diphtheria-tetanus-pertussis-containing vaccine (DTP1), the first dose of measles-containing vaccine (MCV1), and any of the four basic vaccines (bacilli Calmette-Guerin (BCG), oral polio vaccine (OPV0), DTP1, and MCV1), and the corresponding zero-dose estimates independently at a 1 × 1 km resolution and the district level during both time periods. We also explored changes in the factors associated with non-vaccination at the national and regional levels using multilevel logistic regression models. Our results revealed no increases in zero-dose prevalence due to the pandemic at the national level, although considerable increases were observed in a few districts. We found substantial subnational heterogeneities in vaccination coverage and zero-dose prevalence both before and during the pandemic, showing broadly similar patterns in both time periods. Areas with relatively higher zero-dose prevalence occurred mostly in the north and a few places in the south in both time periods. We also found consistent areas of low coverage and high zero-dose prevalence using all three zero-dose indicators, revealing the areas in greatest need. At the national level, risk factors related to socioeconomic/demographic status (e.g., maternal education), maternal access to and utilization of health services, and remoteness were strongly associated with the odds of being zero dose in both time periods, while those related to communication were mostly relevant before the pandemic. These associations were also supported at the regional level, but we additionally identified risk factors specific to zero-dose children in each region; for example, communication and cross-border migration in the northwest. Our findings can help guide tailored strategies to reduce zero-dose prevalence and boost coverage levels in Nigeria.

Predictors for low coverage of uptake of second dose of measles vaccine among children in sub-Saharan Africa, 2023: a systematic review and meta-analysis.

Measles became a public health important disease in sub-Saharan Africa. World Health Organization recommended measles-containing vaccine dose 2 (MCV2) through routine service delivery. This study aims to determine coverage of second-dose measles vaccination uptake and its predictors among children aged 24-35 months in sub-Saharan Africa. We conducted an extensive search of literature as indicated in the guideline of reporting systematic review and meta-analysis (PRISMA). The databases used were PubMed, Google Scholar, and HINARI literature. The overall uptake of the second dose of measles vaccine uptake was 41% (95% CI: 28.90-53.47). Caregiver's awareness of the importance of the second dose of measles (2.51, 95% CI 1.77, 3.25), educational status of mothers (1.30, 95% CI 1.16, 1.45), distance from vaccination site (1.22, 95% CI 1.12, 1.32), and attending four and above ANC visit (2.72, 95% CI 2.29, 3.15) were determinants for second dose measles vaccine uptake. Coverage of the second dose of measles uptake in Sub-Saharan Africa was low (41%) which is lower than the recommendation from WHO. Therefore policymakers and stakeholders should increase mother's awareness. Also, special strategies should be developed for those who are far from the vaccination site. ANC: Ante Natal Care; JBI: Joanna Briggs Institute; MCV1: Measles containing vaccine dose 1; MCV2: Measles containing vaccine dose 2; WHO: World Health Organization.

Evaluating effective measles vaccine coverage in the Malaysian population accounting for between-dose correlation and vaccine efficacy

BackgroundMalaysia introduced the two dose measles-mumps-rubella (MMR) vaccine in 2004 as part of its measles elimination strategy. However, despite high historical coverage of MCV1 and MCV2, Malaysia continues to report high measles incidence. This study suggests a novel indicator for investigating population immunity against measles in the Malaysian population.MethodsWe define effective vaccine coverage (EVC) of measles as the proportion of a population vaccinated with measles-containing vaccine (MCV) and effectively protected against measles infection. A quantitative evaluation of EVC throughout the life course of Malaysian birth cohorts was conducted accounting for both vaccine efficacy (VE) and between-dose correlation (BdC). Measles vaccination coverage was sourced from WHO-UNICEF estimates of Malaysia’s routine immunisation coverage and supplementary immunisation activities (SIAs). United Nations World population estimates and projections (UNWPP) provided birth cohort sizes stratified by age and year. A step wise joint Bernoulli distribution was used to proportionate the Malaysian population born between 1982, the first year of Malaysia’s measles vaccination programme, and 2021, into individuals who received zero dose, one dose and multiple doses of MCV. VE estimates by age and doses received are then adopted to derive EVC. A sensitivity analysis was conducted using 1000 random combinations of BdC and VE parameters.ResultsThis study suggests that no birth cohort in the Malaysian population has achieved > 95% population immunity (EVC) conferred through measles vaccination since the measles immunisation programme began in Malaysia.ConclusionThe persistence of measles in Malaysia is due to pockets of insufficient vaccination coverage against measles in the population. Monitoring BdC through immunisation surveillance systems may allow for the identification of susceptible subpopulations (primarily zero-dose MCV individuals) and increase the coverage of individuals who are vaccinated with multiple doses of MCV. This study provides a tool for assessment of national-level population immunity of measles conferred through vaccination and does not consider subnational heterogeneity or vaccine waning. This tool can be readily applied to other regions and vaccine-preventable diseases.

Progress Toward Measles Elimination - Worldwide, 2000-2022.

Measles is a highly contagious, vaccine-preventable disease that requires high population immunity for transmission to be interrupted. All six World Health Organization regions have committed to eliminating measles; however, no region has achieved and sustained measles elimination. This report describes measles elimination progress during 2000-2022. During 2000-2019, estimated coverage worldwide with the first dose of measles-containing vaccine (MCV) increased from 72% to 86%, then declined to 81% in 2021 during the COVID-19 pandemic, representing the lowest coverage since 2008. In 2022, first-dose MCV coverage increased to 83%. Only one half (72) of 144 countries reporting measles cases achieved the measles surveillance indicator target of two or more discarded cases per 100,000 population in 2022. During 2021-2022, estimated measles cases increased 18%, from 7,802,000 to 9,232,300, and the number of countries experiencing large or disruptive outbreaks increased from 22 to 37. Estimated measles deaths increased 43% during 2021-2022, from 95,000 to 136,200. Nonetheless, an estimated 57 million measles deaths were averted by vaccination during 2000-2022. In 2022, measles vaccination coverage and global surveillance showed some recovery from the COVID-19 pandemic setbacks; however, coverage declined in low-income countries, and globally, years of suboptimal immunization coverage left millions of children unprotected. Urgent reversal of coverage setbacks experienced during the COVID-19 pandemic can be accomplished by renewing efforts to vaccinate all children with 2 MCV doses and strengthening surveillance, thereby preventing outbreaks and accelerating progress toward measles elimination.

New Vaccine Introductions in WHO African Region between 2000 and 2022.

Significant progress has been made in vaccine development worldwide. This study examined the WHO African Region's vaccine introduction trends from 2000 to 2022, excluding COVID-19 vaccines. We extracted data on vaccine introductions from the WHO/UNICEF joint reporting form for 17 vaccines. We examined the frequency and percentages of vaccine introductions from 2000 to 2022, as well as between two specific time periods (2000-2010 and 2011-2022). We analysed Gavi eligible and ineligible countries separately and used a Chi-squared test to determine if vaccine introductions differed significantly. Three vaccines have been introduced in all 47 countries within the region: hepatitis B (HepB), Haemophilus influenzae type b (Hib), and inactivated polio vaccine (IPV). Between 2011 and 2022, HepB, Hib, IPV, the second dose of measles-containing vaccine (MCV2), and pneumococcal conjugate vaccine (PCV) were the five most frequently introduced vaccines. Hepatitis A vaccine has only been introduced in Mauritius, while Japanese encephalitis vaccine has not been introduced in any African country. Between 2000-2010 and 2011-2022, a statistically significant rise in the number of vaccine introductions was noted (p < 0.001) with a significant positive association between Gavi eligibility and vaccine introductions (p < 0.001). Significant progress has been made in the introduction of new vaccines between 2000 and 2022 in the WHO African Region, with notable introductions between 2011 and 2022. Commitments from countries, and establishing the infrastructure required for effective implementation, remain crucial.