Routine Immunization Schedule Research Articles

Immunogenicity evaluation of primary polio vaccination schedule with inactivated poliovirus vaccines and bivalent oral poliovirus vaccine

BackgroundTo assess the immunogenicity of the current primary polio vaccination schedule in China and compare it with alternative schedules using Sabin or Salk-strain IPV (sIPV, wIPV).MethodsA cross-sectional investigation was conducted at four sites in Chongqing, China, healthy infants aged 60–89 days were conveniently recruited and divided into four groups according to their received primary polio vaccination schedules (2sIPV + bOPV, 2wIPV + bOPV, 3sIPV, and 3wIPV). The sero-protection and neutralizing antibody titers against poliovirus serotypes (type 1, 2, and 3) were compared after the last dose.ResultsThere were 408 infants completed the protocol. The observed seropositivity was more than 96% against poliovirus types 1, 2, and 3 in all groups. IPV-only groups induced higher antibody titers(GMT) against poliovirus type 2 (Median:192, QR: 96–384, P<0.05) than the “2IPV + bOPV” group. While the “2IPV + bOPV” group induced significantly higher antibody titers against poliovirus type 1 (Median:2048, QR: 768–2048, P<0.05)and type 3 (Median:2048, QR: 512–2048, P<0.05) than the IPV-only group.ConclusionsOur findings have proved that the two doses of IPV with one dose of bOPV is currently the best polio routine immunization schedule in China.

The Immunogenicity of Monovalent Oral Poliovirus Vaccine Type 1 (mOPV1) and Inactivated Poliovirus Vaccine (IPV) in the EPI Schedule of India.

In 2016, the Global Polio Eradication Initiative (GPEI) recommended the cessation of using type 2 oral poliovirus vaccine (OPV) and OPV, with countries having to switch from the trivalent to bivalent OPV (bOPV) with the addition of inactivated poliovirus vaccine (IPV) in their routine immunization schedule. The current GPEI strategy 2022-2026 includes a bOPV cessation plan and a switch to IPV alone or a combination of vaccine schedules in the future. The focus of our study was to evaluate the immunogenicity of monovalent OPV type 1 (mOPV1) with IPV and IPV-only schedules. This was a three-arm, multi-center randomized-controlled trial conducted in 2016-2017 in India. Participants, at birth, were randomly assigned to the bOPV-IPV (Arm A) or mOPV1-IPV (Arm B) or IPV (Arm C) schedules. Serum specimens collected at birth and at 14, 18, and 22 weeks old were analyzed with a standard microneutralization assay for all the three poliovirus serotypes. The results of 598 participants were analyzed. The type 1 cumulative seroconversion rates four weeks after the completion of the schedule at 18 weeks were 99.5% (97.0-99.9), 100.0% (97.9-100.0), and 96.0% (92.0-98.1) in Arms A (4bOPV + IPV), B (4mOPV1 + IPV), and C (3IPV), respectively. Type 2 and type 3 seroconversions at 18 weeks were 80.0% (73.7-85.1), 76.9% (70.3-82.4); 93.2% (88.5-96.1), 100.0% (98.0-100.0); and 81.9% (75.6-86.8), 99.4% (96.9-99.9), respectively, in the three arms. This study shows the high efficacy of different polio vaccines for serotype 1 in all three schedules. The type 1 seroconversion rate of mOPV1 is non-inferior to bOPV. All the vaccines provide high type-specific immunogenicity. The program can adopt the use of different vaccines or schedules depending on the epidemiology from time to time.

The Last Mile in Polio Eradication: Program Challenges and Perseverance.

As the Global Polio Eradication Initiative (GPEI) strategizes towards the final steps of eradication, routine immunization schedules evolve, and high-quality vaccination campaigns and surveillance systems remain essential. New tools are consistently being developed, such as the novel oral poliovirus vaccine to combat outbreaks more sustainably, as well as non-infectiously manufactured vaccines such as virus-like particle vaccines to eliminate the risk of resurgence of polio on the eve of a polio-free world. As the GPEI inches towards eradication, re-strategizing in the face of evolving challenges and preparing for unknown risks in the post-certification era are critical.

Nature of Television Childbearing Shows and Mode of Delivery Preferences among Primiparous Women in Nairobi, Kenya

Nature of Television Childbearing Shows and Mode of Delivery Preferences among Primiparous Women in Nairobi, Kenya

Expanded spectrum of varicella disease and the need for vaccination in India.

Varicella vaccine was first licensed in Japan and South Korea in 1989 for use in healthy children and was introduced in US in 1995. So far, 29 countries have adopted varicella vaccine in their universal immunization program (UIP). No Asian country, India included, has adopted the varicella vaccine as part of their UIP. The extra-cutaneous sites for VZV diseases are central nervous system and gastrointestinal tract, the expanded disease spectrum includes vasculopathy, myelitis, inflammatory bowel disease, perforated ulcers, and gastritis. The actual disease burden of varicella is not known as most of the infected individuals may not visit the physician. The amplifiable VZV DNA will not always be detectable in cerebrospinal fluid (CSF) samples in protracted illnesses such as vasculopathies, but demonstrable anti-VZV IgG in CSF has diagnostic value. The World Health Organization (WHO) position paper 2014 recommends two doses of varicella and zoster vaccines in targeted population. In India, varicella vaccine is not included in the UIP due to the cost and the belief that lifelong immunity occurs following primary infection. The expanded spectrum of VZV disease and the mounting body of evidence, however, suggest the need for both varicella and zoster vaccines in routine immunization schedule.

Covid-19 Pandemi Sürecinde Sağlıklı Çocuk Takibi ve Kronik Hastalık Kontrollerinin Sürekliliği ve Pandeminin Poliklinik Başvurularına Erken ve Geç Dönemdeki Etkisinin Karşılaştırılması

Aim: Pandemic disrupted health care access in many centers all around the world. CDC recommended that seperating pandemic and non-pandemic hospitals, prioritizing emergency visits, postponing elective operations and, where possible, converting outpatient visits to telehealth calls. In this period, well-child checkups were cancelled and routine childhood vaccination was interrupted. We aimed to evaluate the impact of pandemic on the routine immunization schedule, neonatal screening program, chronic disease follow ups and outpatient clinic visits. &#x0D; Material and Method: In total, 401 children and their parents were included in this study and patient population of interest was children of routine immunization age. Outpatient visit features and compliance with the childhood vaccination and neonatal screening program before and during the pandemic were asked. &#x0D; Results: Compared to 2021, there was a significant increase in both the number of patients with upper respiratory tract infection symptoms and their hospital admissions. While the rates of hospital admissions increased in 2022 in those with diarrhea, almost all of the patients with lower respiratory tract infection symptoms stated that they applied to the hospital in both periods. It was observed that routine vaccination and newborn screening programs were carried out successfully during the pandemic process in Turkey. It was found that chronic disease follow-ups of children were interrupted in 2021. &#x0D; Conclusion: This study has shown how the 3 major components of health system (outpatient clinic visits, well child check-ups and chronic disease follow-ups) were affected at different times of the pandemic in Turkey. Successful management in childhood vaccinations and neonatal screening program should also be ensured in chronic disease follow-up bythe separation of pandemic and non-pandemic hospitals. Showing the strengths and weaknesses of strategies implemented in health system during the pandemic guides the measures to be taken for similar situations that may occur in the future.

Uptake of Human Papilloma Virus vaccine among young women living in fishing communities in Wakiso and Mukono districts, Uganda.

Human Papilloma Virus (HPV) is a preventable cause of cervical cancer, the commonest cancer among women in Uganda. The Uganda Ministry of Health included the HPV vaccine in the free routine immunization schedule since 2015. Five years after this policy, we assessed the uptake of the HPV vaccine and associated socio-demographic factors among young women living in fishing communities in Central Uganda in 2020. We analyzed secondary data from 94 young women aged 9-25 years who were recruited from the two fishing communities (Kasenyi landing site and Koome Island) in a primary study that aimed to promote awareness of maternal and childhood vaccines. We assessed uptake of the HPV vaccine as the proportion of participants who self-reported to have ever received at least one dose of the HPV vaccine. We assessed the socio-demographic factors associated with HPV vaccine uptake using a modified Poisson regression model adjusted for clustering by study site in STATA version 17. The mean (standard deviation) age of study participants was 21.1 (3.1) years and most (81.9%) of them were from Kasenyi landing site. The uptake of the HPV vaccine was 10.6% [95% Confidence Interval (CI) 5.6, 18.9]. After adjusting for covariates, being 13-19 years old (adjusted prevalence ratio [aPR] 5.52, 95%CI 1.69, 18.00) and of Catholic religion (aPR 5.55, 95%CI 1.53, 20.16) were significantly associated with HPV vaccine uptake. The HPV vaccine uptake was very low, despite the reported 99% national coverage of HPV vaccination program for the first dose at the end of 2019. Age and religion showed to be important determinants of the HPV vaccine uptake. Reasons for such very low uptake of HPV vaccinations need to be carefully assessed to find effective strategies to improve it.

The Global Demand and Supply Balance of the Human Papillomavirus Vaccine: Implications for the Global Strategy for the Elimination of Cervical Cancer.

As of November 2023, 140 World Health Organization (WHO) member states had introduced human papillomavirus (HPV) vaccination in their routine immunization schedules. Despite a continuously increasing demand from countries across all income groups, supply constraints, COVID-19 pandemic disruptions, and other factors have slowed the pace of introduction, particularly in low-resource settings. Using a population-based forecasting methodology and leveraging the WHO's yearly vaccine supply data collection, we updated global demand and supply projections for the HPV vaccine for the period of 2022-2031. The analysis aimed at clarifying the magnitude of the challenges to bringing in equitable access to HPV vaccines, which can hinder the achievement of the Global Strategy for the Elimination of Cervical Cancer. The results of this analysis show that the risk of HPV shortages has significantly decreased, and global supply is now, under normal circumstances, sufficient to meet global demand. In the long term, HPV supply will be more than sufficient to meet the Global Strategy's goal of 90% of girls fully vaccinated with the HPV vaccine by the age of 15 years. Nonetheless, paying attention to the formulation of policies and carefully managing demand and supply will be required to ensure the long-term sustainability of the HPV vaccine program.

Neutralizing anti-polio antibody titre in newborn babies in post-polio eradication period in Nigeria

BackgroundAccording to Polio Eradication and Endgame Strategic Plan 2019-2023 (PEESP), countries that achieved wild polio elimination is expected to replace oral polio vaccine (OPV) which has a risk of vaccine-derived poliovirus, Inactivated Polio Vaccine (IPV). It is important to determine the earliest time in the age of a child at which IPV could be introduced into the country’s routine immunization schedule for effectiveness especially as it concerns neutralizing effect of trans-placental transmitted antibodies which usually does not affect OPV. In this study, the level of poliovirus neutralizing antibody titre among neonates at birth was evaluated. MethodsA cross-sectional study of mother-baby pair. The serum level of the neutralizing Poliovirus antibody IgG titre was done by the Enzyme Linked Immunosorbent Assay (ELISA) technique. ResultsThere was 100% transfer of maternal passive antibodies to their babies. The mean poliovirus antibody titre among neonates was 21.8 IU/L which was above the neutralizing titre level. Most (85.7%) babies antibody level correlate positively with that of their mothers. ConclusionThe transferred maternal antibodies to the babies are still very high at birth, and capable of dampening the immunity of IPV if introduced early. Programme managers should evaluate the impact and benefit of given booster dose of IPV to pregnant mothers to increase the titre level in their babies. This will be very necessary when the OPV is withdrawn from the immunization schedule.

Persistence of immunity following a single dose of inactivated poliovirus vaccine: a phase 4, open label, non-randomised clinical trial

The polio eradication endgame required the withdrawal of Sabin type 2 from the oral poliovirus vaccine and introduction of one or more dose of inactivated poliovirus vaccine (IPV) into routine immunisation schedules. However, the duration of single-dose IPV immunity is unknown. We aimed to address this deficiency. In this phase 4, open-label, non-randomised clinical trial, we assessed single-dose IPV immunity. Two groups of infants or children were screened: the first group had previously received IPV at 14 weeks of age or older (previous IPV group; age >2 years); the second had not previously received IPV (no previous IPV group; age 7-12 months). At enrolment, all participants received an IPV dose. Children in the no previous IPV group received a second IPV dose at day 30. Blood was collected three times in each group: on days 0, 7, and 30 in the previous IPV group and on days 0, 30, and 37 in the no previous IPV group. Poliovirus antibody was measured by microneutralisation assay. Immunity was defined as the presence of a detectable antibody or a rapid anamnestic response (ie, priming). We used the χ2 to compare proportions and the Mann-Whitney U test to assess continuous variables. To assess safety, vaccinees were observed for 30 min, caregivers for each participating child reported adverse events after each follow-up visit and were questioned during each follow-up visit regarding any adverse events during the intervening period. Adverse events were recorded and graded according to the severity of clinical symptoms. The study is registered with ClinicalTrials.gov, NCT03723837. From Nov 18, 2018, to July 31, 2019, 502 participants enrolled in the study, 458 (255 [65%] boys and 203 [44%] girls) were included in the per protocol analysis: 234 (93%) in the previous IPV group and 224 (90%) in the no previous IPV group. In the previous IPV group, 28 months after one IPV dose 233 (>99%) of 234 children had persistence of poliovirus type 2 immunity (100 [43%] of 234 children were seropositive; 133 [99%] of 134 were seronegative and primed). In the no previous IPV group, 30 days after one IPV dose all 224 (100%) children who were type 2 poliovirus naive had seroconverted (223 [>99%] children) or were primed (one [<1%]). No adverse events were deemed attributable to study interventions. A single IPV dose administered at 14 weeks of age or older is highly immunogenic and induces nearly universal type 2 immunity (seroconversion and priming), with immunity persisting for at least 28 months. The polio eradication initiative should prioritise first IPV dose administration to mitigate the paralytic burden caused by poliovirus type 2. WHO and Rotary International.

Exploring Shigella vaccine priorities and preferences: Results from a mixed-methods study in low- and middle-income settings

BackgroundShigella is the leading bacterial cause of diarrheal mortality in children and can cause long-term effects on growth and development. No licensed Shigella vaccines currently exist but several promising candidates are in development and could be available in the next five years. Despite Shigella being a well-known public health target of the World Health Organization for decades, given current burden estimates and competing preventable disease priorities in low-income settings, whether the availability of an effective Shigella vaccine will lead to its prioritization and widespread introduction among countries at highest risk is unknown. MethodsWe conducted a mixed-methods study of national stakeholders and healthcare providers in five countries in Asia and Africa and regional stakeholders in the Pan American Health Organization to identify preferences and priorities for forthcoming Shigella vaccines. ResultsIn our study of 89 individuals, diarrhea was the most frequently mentioned serious health concern for children under five years. Antimicrobial resistance (AMR) was more often considered very concerning than diarrhea or stunting. Shigella awareness was high but not considered a serious health concern by most stakeholders. Most participants were willing to consider adding a new vaccine to the routine immunization schedule but expressed reservations about a Shigella vaccine because of lower perceived burden relative to other preventable diseases and an already crowded schedule; interest was highest among national stakeholders in countries receiving more financial support for immunization. The priority of a Shigella vaccine rose when participants considered vaccine impacts on reducing stunting and AMR. Participants strongly preferred oral and combination vaccines compared to injectable and a single-antigen presentations, citing greater perceived community acceptability. ConclusionsThis study provides a critical opportunity to hear directly from country and regional stakeholders about health priorities and preferences around new vaccines. These findings should inform ongoing Shigella vaccine development efforts and eventual vaccine introduction and implementation planning.

Vaccination schedule for adolescents. Consensus of the AEV, CAV-AEP and SEMA

We present the consensus document on the immunization schedule for adolescents developed by 3 scientific societies: the Spanish Association of Pediatrics (AEP), through its Advisory Committee on Vaccines (CAV-AEP), the Spanish Society of Adolescent Medicine (SEMA) and the Spanish Association of Vaccinology (AEV). There are particularities in infectious disease during adolescence, such as an increased susceptibility to pertussis, poorer outcomes of chickenpox, mumps and hepatitis A, a high incidence of sexually transmitted infections or increased prevalence of meningococcal carriage. The document analyses the schedule for adolescents in the context of vaccination policy overall. It contemplates the vaccines to be included in the immunization schedule for healthy adolescents: against invasive meningococcal disease (tetravalent ACWY and B), against human papillomavirus (which should be gender-neutral), against pertussis, against influenza and against SARS-CoV-2 (in unvaccinated individuals and at-risk groups). It is worth noting that the 4CMenB vaccine appears to confer some protection against gonococcal infection, which would be a considerable added value for adolescents. The vaccination of adolescents belonging to risk groups or travelling abroad also needs to be contemplated, as is the case in any other age group. Vaccination against hepatitis A, which is included in the routine immunization schedule of Catalonia, Ceuta and Melilla from the second year of life, should also be considered a priority in adolescents traveling to endemic areas.

The association between vaccine hesitancy and pertussis: a systematic review and meta-analysis

BackgroundRobust routine immunization schedules for pertussis-containing vaccines have been applied for years, but pertussis outbreaks remain a worldwide problem. This study aimed to investigate the association between vaccine hesitancy and pertussis in infants and children.MethodsWe searched PubMed, Cochrane, Web of Science, Embase, and China National Knowledge Internet for studies published between January 2012 and June 2022. This study included case–control and cohort studies that assessed the association between childhood/maternal vaccine hesitancy and odds ratios (ORs), risk ratios (RRs), and vaccine effectiveness (VE) related to pertussis in infants and children le 9 years old. ORs/VEs with a 95% confidence interval (CI) were calculated. Random-effects meta-analysis models were used for appropriate pooled estimates, and heterogeneity was assessed using {I}^{2}. Cumulative meta-analysis and subgroup analyses stratified by study characteristics were performed.ResultsTwenty-two studies were included, with a mean quality score of 7.0 (range 6.0–9.0). Infants and children with pertussis were associated with higher vaccine hesitancy to all doses (OR = 4.12 [95% CI: 3.09–5.50]). The highest OR was between children who were unvaccinated over four doses and children who were fully vaccinated (OR = 14.26 [95%CI: 7.62–26.70]); childhood vaccine delay was not statistically significantly associated with pertussis risk (OR = 1.18 [95% CI: 0.74–1.89]). Maternal vaccine hesitancy was associated with significantly higher pertussis risk in infants aged 2 and 3 months old, with higher pertussis ORs in infants le 2 months old (OR = 6.02 [95%CI: 4.31–8.50], OR = 5.14 [95%CI: 1.95–13.52] for infants le 2 and le 3 months old, respectively). Maternal and childhood VEs were high in reducing pertussis infection in infants and children. The administration time of maternal vaccination had little effect on VE.ConclusionVaccine hesitancy increased pertussis risks in infants and children. Ensuring that children receive up-to-date pertussis vaccines is essential; short delays in receiving childhood vaccinations may be unimportant. Maternal vaccinations for pertussis should be encouraged.

Status of New Vaccine Introduction - Worldwide, 2016-2021.

This report describes the status of introductions globally for eight World Health Organization (WHO)-recommended new and underutilized vaccines, comprising 10 individual vaccine antigens. By 2021, among 194 countries worldwide, 33 (17%) provided all of these 10 WHO-recommended antigens as part of their routine immunization schedules; only one low-income country had introduced all of these recommended vaccines. Universal hepatitis B birth dose; human papillomavirus vaccine; rotavirus vaccine; and diphtheria, tetanus, and pertussis-containing vaccine first booster dose have been introduced by 57%, 59%, 60%, and 72% of all countries worldwide, respectively. Pneumococcal conjugate vaccine, rubella-containing vaccine, measles-containing vaccine second dose, and Haemophilus influenzae type b vaccine have been introduced by 78%, 89%, 94%, and 99% of all countries, respectively. The annual rate of new vaccine introductions declined precipitously when the COVID-19 pandemic started, from 48 in 2019 to 15 in 2020 before rising to 26 in 2021. Increased efforts to accelerate new and underutilized vaccine introductions are urgently needed to improve universal equitable access to all recommended vaccines to achieve the global Immunization Agenda 2021-2030 (IA2030) targets.

Study protocol for a cluster-randomised controlled trial of hybrid parents and health workers adaptive intervention for optimal routine childhood immunisation coverage in the communities of Ebonyi state, Nigeria: the AGINTOPIC trial protocol

IntroductionVaccine-preventable infectious diseases (VPDs) are major causes of morbidity/mortality among children under 5 years of age worldwide and in Nigeria/Ebonyi state. Routine childhood immunisation is an invaluable prevention strategy for...

Calendario de vacunaciones del adolescente. Consenso AEV, CAV-AEP y SEMA

We present the consensus document on the immunization schedule for adolescents developed by 3 scientific societies: the Spanish Association of Pediatrics (AEP), through its Advisory Committee on Vaccines (CAV-AEP), the Spanish Society of Adolescent Medicine (SEMA) and the Spanish Association of Vaccinology (AEV). There are particularities in infectious disease during adolescence, such as an increased susceptibility to pertussis, poorer outcomes of chickenpox, mumps and hepatitis A, a high incidence of sexually transmitted infections or increased prevalence of meningococcal carriage. The document analyses the schedule for adolescents in the context of vaccination policy overall. It contemplates the vaccines to be included in the immunization schedule for healthy adolescents: against invasive meningococcal disease (tetravalent ACWY and B), against human papillomavirus (which should be gender-neutral), against pertussis, against influenza and against SARS-CoV-2 (in unvaccinated individuals and at-risk groups). It is worth noting that the 4CMenB vaccine appears to confer some protection against gonococcal infection, which would be a considerable added value for adolescents. The vaccination of adolescents belonging to risk groups or travelling abroad also needs to be contemplated, as is the case in any other age group. Vaccination against hepatitis A, which is included in the routine immunization schedule of Catalonia, Ceuta and Melilla from the second year of life, should also be considered a priority in adolescents traveling to endemic areas.

Community Barriers, Enablers, and Normative Embedding of Second Year of Life Vaccination in Ghana: A Qualitative Study.

Coverage rates for second year of life (2YL) vaccination still lag behind infant vaccination in most settings. We conducted a qualitative baseline study of community barriers and enablers to acceptance of 2YL vaccines in Ghana 4 years after introducing the second dose of the measles-containing vaccine. We conducted 26 focus group discussions in 2016 with men and women caregivers from mixed urban, peri-urban, and rural areas, as well as pastoralists, using semistructured topic guides based on the Health Belief Model theory. We conducted a thematic analysis of the discussion using NVivo software. We use Normalization Process Theory to contextualize results as a snapshot of a dynamic process of community adaptation to change to a well-established routine immunization schedule following 2YL introduction. Routine immunization for infants enjoys resilient demand, grounded in strong community norms despite surprisingly low levels of vaccine literacy. Despite best practices like integration with the established 18-month "weighing visit," demand for 2YL vaccination is still conditional on individual awareness and competition for limited maternal time, household resources, and other health concerns. An embedded norm that children should be fully vaccinated by 12 months originally sustained Expanded Programme for Immunization goals but now discouraged some caregivers from seeking vaccines for children perceived to be "too old" to vaccinate. Caregivers cited greater costs and inconvenience of taking older, heavier children in for vaccination and anticipated criticism from both community members and health care providers for coming "too late." Closing the 2YL vaccination coverage gap will ultimately require modifying embedded norms among caregivers and health care providers alike. Time is necessary but not sufficient to reach this goal. Progress can be accelerated by increasing the level of community and institutional engagement and adapting services where possible to minimize added costs to caregivers of vaccinating older children.

EPH46 The Association between Vaccine Hesitancy and Pertussis: A Systematic Review and Meta-Analysis

Robust routine immunization schedules of pertussis-containing vaccines have been applied for years, but the pertussis outbreak is still a worldwide problem. This study aimed to explore the association between vaccine hesitancy and pertussis in infants and children.

Analysis of population immunity to poliovirus following cessation of trivalent oral polio vaccine.

The global withdrawal of trivalent oral poliovirus vaccine (OPV) (tOPV, containing Sabin poliovirus strains serotypes 1, 2 and 3) from routine immunization, and the introduction of bivalent OPV (bOPV, containing Sabin poliovirus strains serotypes 1 and 3) and trivalent inactivated poliovirus vaccine (IPV) into routine immunization was expected to improve population serologic and mucosal immunity to types 1 and 3 poliovirus, while population mucosal immunity to type 2 poliovirus would decline. However, over the period since tOPV withdrawal, the implementation of preventive bOPV supplementary immunization activities (SIAs) has decreased, while outbreaks of type 2 circulating vaccine derived poliovirus (cVDPV2) have required targeted use of monovalent type 2 OPV (mOPV2). We develop a dynamic model of OPV-induced immunity to estimate serotype-specific, district-level immunity for countries in priority regions and characterize changes in immunity since 2016. We account for the changes in routine immunization schedules and varying implementation of preventive and outbreak response SIAs, assuming homogenous coverages of 50% and 80% for SIAs. In areas with strong routine immunization, the switch from tOPV to bOPV has likely resulted in gains in population immunity to types 1 and 3 poliovirus. However, we estimate that improved immunogenicity of new schedules has not compensated for declines in preventive SIAs in areas with weak routine immunization. For type 2 poliovirus, without tOPV in routine immunization or SIAs, mucosal immunity has declined nearly everywhere, while use of mOPV2 has created highly heterogeneous population immunity for which it is important to take into account when responding to cVDPV2 outbreaks. The withdrawal of tOPV and declining allocations of resources for preventive bOPV SIAs have resulted in reduced immunity in vulnerable areas to types 1 and 3 poliovirus and generally reduced immunity to type 2 poliovirus in the regions studied, assuming homogeneous coverages of 50% and 80% for SIAs. The very low mucosal immunity to type 2 poliovirus generates substantially greater risk for further spread of cVDPV2 outbreaks. Emerging gaps in immunity to all serotypes will require judicious targeting of limited resources to the most vulnerable populations by the Global Polio Eradication Initiative (GPEI).

Long-term measles antibody profiles following different vaccine schedules in China, a longitudinal study

Characterizing the long-term kinetics of maternally derived and vaccine-induced measles immunity is critical for informing measles immunization strategies moving forward. Based on two prospective cohorts of children in China, we estimate that maternally derived immunity against measles persists for 2.4 months. Following two-dose series of measles-containing vaccine (MCV) at 8 and 18 months of age, the immune protection against measles is not lifelong, and antibody concentrations are extrapolated to fall below the protective threshold of 200 mIU/ml at 14.3 years. A catch-up MCV dose in addition to the routine doses between 8 months and 5 years reduce the cumulative incidence of seroreversion by 79.3–88.7% by the age of 6 years. Our findings also support a good immune response after the first MCV vaccination at 8 months. These findings, coupled with the effectiveness of a catch-up dose in addition to the routine doses, could be instrumental to relevant stakeholders when planning routine immunization schedules and supplemental immunization activities.