Vaccination History Research Articles

Vaccination Coverage for Medically Indicated Vaccines in a Convenience Sample of Severely Immunocompromised Patients with COVID-19: An Observational Cohort Study

Background: In recent decades, the number of immunocompromised patients (ICPs) has increased significantly. ICPs have an impaired immune system, making them susceptible to complicated infections. To protect them from infections, ICPs are eligible to receive several medically indicated vaccines. To obtain insight into the uptake of these medically indicated vaccines, we determined the coverage of these vaccines in ICPs. Methods: This observational cohort study was conducted at the University Medical Centre Utrecht, the Netherlands, from September 2021 to April 2022. All adult ICPs admitted for COVID-19 were asked to complete a questionnaire on their vaccination history (pneumococcal, herpes zoster, human papillomavirus vaccination, influenza, and COVID-19 vaccines) and history of vaccine-preventable infections. In addition, patients’ vaccination history was reviewed in medical files. Results: A total of 115 patients completed the questionnaire and were included. Although all patients had an indication for pneumococcal vaccination, only 22 received it (19%). Coverage for herpes zoster was low (1%, 1/106 eligible patients). Coverage for human papillomavirus vaccination (HPV) was also low (40%, two out of five eligible patients). In contrast, 92% of patients received vaccination against SARS-CoV-2, and 77% of patients received seasonal influenza vaccination. Conclusions: Although coverage for influenza and COVID-19 vaccination was high in ICPs, coverage for other medically indicated vaccines was low. Identifying which factors contributed to high COVID-19 and influenza vaccine uptake can help to improve vaccination rates for the other recommended vaccines. Clear guidelines for clinicians and the removal of organizational obstacles are needed to improve vaccination coverage.

Vaccine Therapies for Prostate Cancer: Current Status and Future Outlook

Prostate cancer is a prevalent cancer in elderly men, and immunotherapy has emerged as a promising treatment approach in recent years. The aim of immunotherapy is to stimulate the body’s immune system to target and destroy cancer cells. Cancer vaccines that are highly specific, safe, and capable of creating long-lasting immune responses are a key focus in cancer immunotherapy research. Despite progress in clinical trials showing positive results, the practical use of cancer vaccines still encounters various obstacles. The complexity of the immune microenvironment and variations in the immune systems of individual patients have hindered the progress of research on prostate cancer vaccines. This review examines the history and mechanisms of cancer vaccines, summarizes recent clinical research findings, and explores future directions in the development of prostate cancer vaccines.

Trends in the epidemiology of pertussis in Malaga, Spain (2017-2024)

Description of the epidemiological evolution of pertussis in the province of Malaga, Spain (2017 - 2024), disease severity, and vaccination coverage. A cross-sectional study was conducted using reported cases from the Andalusian Notifiable Diseases Network (RedAlerta). The incidence of pertussis was calculated per 100,000 inhabitants for each health district, quarter, and year. Additionally, the relationship between severe cases (hospitalizations) and vaccination status was analyzed. A total of 181 pertussis cases were identified. Of these, 56.4% were reported during the pre-pandemic period (2017-2019), while 9.95% occurred between 2020 and 2023. An increase in cases was observed in the first quarter of 2024 (n = 61; 33.7% of the total cases), compared to previous years (1 to 46 cases). The 0 to 20-year group accounted for 71.3% of cases, of which 57.4% had received at least partial vaccination prior to contracting pertussis. Severe disease requiring hospitalization occurred in 25.6% of cases, with a higher frequently among unvaccinated individuals (70% vs 18.3%; p < 0.001). Among hospitalized cases, 42.4% had not received any prior doses of the vaccine. Additionally, 47.1% of the 17 pertussis cases in children aged =1 year had not received any vaccination and had no history of maternal vaccination during pregnancy. An increase in reported pertussis cases is observed in early 2024 in Malaga, but hospitalization rates among confirmed cases remained stable. A significant association is found between prior vaccination against pertussis and reduced disease severity (hospitalization) in the 0 to 20-year-old age group.

Evaluation of Heath Care Commitment with Prevention and Infectious Control Protocols in Mofid Children Hospital, IRAN

Background: The dedication of healthcare teams to adhering to protocols for the use of personal protective equipment (PPE), maintaining vaccination coverage among healthcare workers (HCWs), and ensuring environmental health are crucial elements in managing hospital-acquired infections. Objectives: This study aimed to evaluate adherence to PPE use, vaccination history, hand hygiene protocols, and environmental health practices in a tertiary children's hospital in Iran. Methods: This cross-sectional study evaluated compliance with PPE use, vaccination history among doctors, nurses, and hospital staff, adherence to strict hygiene practices, patient isolation protocols, and environmental health measures based on an Iranian Health Ministry query. Data collection was conducted over three months, from May to August 2023. Results: During the study, 285 staff members were assessed for compliance with hand hygiene protocols. Nurses demonstrated the highest level of compliance, reaching 51%. The highest compliance with hand hygiene protocols at the five designated moments was approximately 79%, with the transplantation and hemodialysis wards achieving the highest rates. Nurses also showed the most positive vaccination records. Personal protective equipment was used correctly in various wards, with an overall compliance rate of 79%. Conclusions: This study revealed that compliance with health protocols in different parts of the hospital was suboptimal and required significant improvement.

Tetanus Vaccination in Agricultural Workers: A Retrospective Study on Seroprevalence over 10 Years

Background/Objectives: Tetanus is a serious, non-contagious infection caused by Clostridium tetani, which remains a global health threat despite the availability of an effective vaccine. The current state of immunization for agricultural workers in Italy reveals significant disparities, reflecting a non-homogeneous distribution of vaccination coverage across regions and subgroups. The aim of the study was to investigate the prevalence of tetanus antibodies in a cohort of agricultural workers in Eastern Sicily in order to evaluate possible public health strategies for improving vaccination coverage. Methods: This observational retrospective study assessed tetanus immunization coverage in agricultural workers in Eastern Sicily during the period from 2012–2022. Results: A total of 1143 workers participated, of which 71% (n = 871) had protective tetanus antitoxin levels. Of the 835 vaccinated workers, 9% were not immune, while 19% of those who were not vaccinated or did not recall their vaccination history were immune. Significant gaps in vaccination were noted, particularly among non-European workers, with only 23% vaccinated compared to 89% of European workers. Additionally, vaccination rates were higher in those born after 1963, when vaccination became mandatory. Conclusions: The results underscore the need for targeted vaccination strategies, especially for older and migrant workers, as well as the importance of workplace immunization programs led by occupational physicians. Improving vaccination coverage among agricultural workers is essential for preventing tetanus infections in high-risk agricultural populations.

Assessment of mumps virus-specific antibodies: comparison of three different enzyme immunoassays and neutralization test

IntroductionWe evaluated the application of a newly improved enzyme immunoassay (EIA) kit, Mumps IgG Seiken®, by comparing antibody responses to different EIA kits, and neutralization tests (NTs), using clinical samples. MethodsSerum samples were collected before and 4-6 weeks after vaccination from 128 children who had no history of mumps or mumps vaccination. Using three different EIA kits, Mumps IgG Seiken®, a commercial kit from Enzygnost®, and an in-house kit, mumps-specific IgG antibodies were measured. Anti-mumps antibody responses between each of the EIA kits and NTs were evaluated. ResultsBefore vaccination, all samples were seronegative, except for three serum samples measured by Mumps IgG Seiken®, which exhibited equivocal. The antibody-positivity rates and equivocal rates of Mumps IgG Seiken® post-vaccination (71.1% and 23.4%, respectively) were comparable to those of Enzygnost® (74.2% and 19.5%, respectively). However, antibody-positivity and equivocal rates were significantly higher and lower than those of in-house kit (51.6% and 40.6%, respectively) (p<0.05). The concordance rates of the kit (68.7%) were comparable to those of Enzygnost® (71.1%) and higher than those of in-house-developed kit (58.6%) (p<0.05). The area under curve of the three EIA kits were 0.801, 0.804, and 0.859; however, the differences did not reach significance. Correlations of the values obtained using three EIA kits with NTs were 0.71, 0.61, and 0.78. ConclusionThe newly approved Mumps IgG Seiken® showed good correlation with NTs and had lower equivocal rates compared to in-house kit, comparable to Enzygnost®. This kit may be clinically acceptable for the evaluation of vaccine immunogenicity.

Effectiveness of the 2023-2024 Omicron XBB.1.5-containing mRNA COVID-19 vaccine (mRNA-1273.815) in preventing COVID-19-related hospitalizations and medical encounters among adults in the United States

Effectiveness of the 2023-2024 Omicron XBB.1.5-containing mRNA COVID-19 vaccine (mRNA-1273.815) in preventing COVID-19-related hospitalizations and medical encounters among adults in the United States

Anti-Tetanus Vaccination Is Associated with Reduced Occurrence and Slower Progression of Parkinson’s Disease—A Retrospective Study

Background: Parkinson’s disease (PD) is a neurodegenerative disorder that progressively damages the autonomic and central nervous systems, leading to hallmark symptoms such as resting tremor, bradykinesia, and rigidity. Despite extensive research, the underlying cause of PD remains unclear, and current treatments are unable to halt the progression of the disease. In this retrospective study, based on historical electronic health records (EHR) from a national health provider covering the period from 2003 to 2023, we investigated the impact of vaccination and medication purchases on PD occurrence and severity. Methods: Using a case–control design, we compared the vaccination histories of 1446 PD patients with 7230 matched controls to assess the association between vaccination and PD onset. Additionally, we explored statistical associations between vaccination, medication purchases, and PD severity over an average of 9 years of follow-up, utilizing a machine learning algorithm to quantify disease severity based on annual antiparkinsonian medication purchases.Results: Our analysis revealed a significant reduction in PD occurrence following tetanus–diphtheria (Td) vaccination, with an adjusted odds ratio of 0.17 (95% CI [0.04, 0.70]) for PD onset within 5 years post-vaccination. Furthermore, a time-dependent relationship was identified between the duration since vaccination and both the rate of PD onset and disease progression. Notably, we observed that antimicrobial treatments significantly influenced disease severity, consistent with the antibiotic sensitivity profile of Clostridium tetani. Conclusions: These findings support the hypothesis that tetanus vaccination and/or C. tetani eradication may reduce PD occurrence and slow its progression, suggesting promising directions for future research in PD prevention and treatment.

Understanding the public's decision-making about seasonal flu vaccination during a pandemic: Application of the precaution adoption process model.

Understanding the behavioural factors influencing flu vaccination is crucial for mitigating seasonal infection outbreaks. This study utilised the Precaution Adoption Process Model (PAPM) to examine the public's decision-making about seasonal flu vaccination through an online cross-sectional survey with 2004 participants in England, UK. Results showed varying stages of decision-making: 7% in Stage 2 (unengaged), 10% in Stage 3 (undecided), 7% in Stage 4 (decided not to vaccinate), 39% in Stage 5 (decided to vaccinate) and 38% in Stage 6 (vaccinated). Regression modelling revealed factors common across stages and unique to certain stages, such as flu vaccination history distinguishing those who received the vaccine. Vaccine knowledge (Stage 2), perceived benefits (Stage 4), perceived control and fear of needles (Stage 5) were uniquely associated with specific PAPM stages. The study discusses policy implications for integrating these findings to improve flu vaccination uptake, highlighting the importance of tailored strategies based on decision-making stages.

The association of medical and vaccination history with the development of long COVID

The association of medical and vaccination history with the development of long COVID

Bias and negative values of COVID-19 vaccine effectiveness estimates from a test-negative design without controlling for prior SARS-CoV-2 infection

Test-negative designs (TNDs) are used to assess vaccine effectiveness (VE). Protection from infection-induced immunity may confound the association between case and vaccination status, but collecting reliable infection history can be challenging. If vaccinated individuals have less infection-induced protection than unvaccinated individuals, failure to account for infection history could underestimate VE, though the bias is not well understood. We simulated individual-level SARS-CoV-2 infection and COVID-19 vaccination histories and a TND. VE against symptomatic infection and VE against severe disease estimates unadjusted for infection history underestimated VE compared to estimates adjusted for infection history, and unadjusted estimates were more likely to be below 0%, which could lead to an incorrect interpretation that COVID-19 vaccines are harmful. TNDs assessing VE immediately following vaccine rollout introduced the largest bias and potential for negative VE against symptomatic infection. Despite the potential for bias, VE estimates from TNDs without prior infection information are useful because underestimation is rarely more than 8 percentage points.

Serological evidence of natural exposure to rabies in rural populations in Gabon.

Rabies is one of the oldest known zoonotic diseases, with dogs being the main reservoir for 99% of the cases of human rabies. However, wild animals may also be rabies vectors. In most cases, contact with a rabid animal results in rabies without pre- or post-exposure prophylaxis, and the disease is nearly always fatal. Nevertheless, a few studies have documented cases of rabies-specific antibodies detection in people with no history of vaccination, suggesting that individuals can be in contact with the virus without developing fatal rabies. To further investigate this possibility of non-lethal human rabies exposure, we carried out a retrospective serological analysis, using both immunoassays (ELISA) and seroneutralization assays (RFFIT), on 430 sera collected between 2005 and 2008 from rural unvaccinated Gabonese populations in the Estuaire and Ogooué-Ivindo provinces. Eleven (11) samples (2.5%) were positive for rabies-specific antibodies using both techniques: 1 in Estuaire and 10 in Ogooué-Ivindo. One of three positive people from the Ogooué-Ivindo province, resampled in early 2023, was still positive for rabies-specific antibodies, suggesting that some degree of immunity can be maintained over many years. Our results also show a marginally significant higher prevalence among hunters. This study demonstrates that rabies circulates actively in Gabon and some unvaccinated individuals living in rural environments can be exposed to the virus and survive, with the development of a significant and specific humoral response that can persist for more than 15 years. This passive seroprevalence survey underlines the need to establish a national surveillance system of rabies in both humans and animals in urban and rural areas, and to enhance access to pre- and post-exposure prophylaxis.

Rubella antibody levels in the healthy Chinese population: a meta-analysis.

To gain a comprehensive understanding of rubella seroprevalence in the healthy population in China and to offer data-driven support for the goal of rubella elimination. CNKI, Wanfang database, VIP database, CBM, PubMed, web of Science, and Embase databases were searched to collect studies reporting the positive rate of rubella antibody among the Chinese healthy populations between 2001 and 2022. We conducted a meta-analysis using R language, and data were combined using random effects model. A total of 97 studies were included, encompassing a sample size of 103,018. Meta-analysis showed that the overall prevalence of rubella antibody positivity in the Chinese healthy population was 77.29% (95% CI: 75.26-79.33). The prevalence of rubella antibody varied significantly based on age and vaccination status. Among the age groups studied, the <1-year-old group exhibited the lowest positivity rate for rubella antibody at 47.87% (95% CI: 41.53-54.21),while the ≥50 years old group showed the highest positivity rate at 85.43% (95% CI: 81.01-89.85); individuals with a history of vaccination demonstrated a higher antibody positivity rate compared to those without vaccination history. The prevalence of rubella antibody in healthy Chinese population is relatively low. In order to establish a solid immunity threshold levels, it requires conducting timely immunization programs on key groups such as middle school students and the women of childbearing age on the basis of ensuring a high level of rubella-containing-vaccines (RCV) coverage, so as to achieve the goal of eliminating rubella. https://www.crd.york.ac.uk/PROSPERO/, identifier CRD42024607949.

Analysis of the current status of the protection in children from of polio

Introduction. There is a risk of an exponential increase in the incidence of polio in the world, if there is a deviation from the current plan of measures to localize endemic areas of polio and until global eradication of the virus achieved. Routine immunization against polio and widespread vaccination is the main goal of the polio control strategy. There is currently no need to strengthen planned vaccination work in Russia to consolidate the results of the polio control program, as evidenced by the data of dynamic serological monitoring. Aim: Evaluate the level of seroconversion after administration of poliovaccine and the duration of protective antibody titer maintenance in children. Materials and methods. A single-stage, single-center determination of the titer of antibodies to poliovirus types 1 and 3 was carried out using the neutralization method. There were studied 162 samples collected as part of the assignment from the Center of Hygiene and Epidemiology of the Republic of Buryatia (1.44% of the pediatric population of the children’s polyclinic): three groups of 1–2 years, 3–4 years and 15–17 years children. The average age in the group 1 was 1.64 ± 0.48 years, group 2 — 3.48 ± 0.54 years, and group 3 — 15.38 ± 0.67 years. Medical documentation was analyzed and compared: completed preventive vaccination cards (form 063/u) and preventive vaccination sheet in the child development card (form 112/u) for a complete collection children’s vaccination history. Results. Deviations of vaccination dates from the current national calendar of preventive vaccinations noted in all age groups with a high frequency. In our analysis, 100% of children demonstrate the presence of protective antibodies to poliomyelitis types 1 and 3. The duration of preservation of neutralizing antibodies is 13.05 ± 0.94 years, with an average of 9–15 years. Conclusion. The analyzed serological monitoring of postvaccinal immunity to poliomyelitis testifies to the high efficiency of the preventive work.

Examining the Effect of Parental COVID-19 Vaccination Prior to Birth and the Association Between COVID-19 and Cancer in Children Under Six.

The biology of COVID-19 has intricate links to childhood cancer, exacerbated by pandemic disturbances. This research aims to explore the association between childhood cancer in children under 6 years old and COVID-19 immunisation, in addition to the effects of vaccination on parents before delivery. The study employs a case-control approach, gathering informed consent and matching factors like age, marital status, and socioeconomic status between cases and controls. A survey was distributed, culminating in 191 children under six, with data from 136 diagnosed cancer cases collected in 2023, adhering to methodological standards in epidemiological research. The analysis utilised SPSS28, employing chi-square testing and logistic regression. Chi-square testing confirmed a significant rise in childhood cancer rates post-COVID-19 pandemic compared to pre-pandemic rates. Key factors influencing cancer incidence include the mother's age at childbirth, parental vaccination history before pregnancy, maternal vaccination details during pregnancy, the child's COVID-19 infection status, and maternal marriage age. Notably, younger mothers faced higher COVID-19 infection risks, but vaccination appears to mitigate paediatric cancer risk. The post-pandemic surge in childhood cancer underscores a complex interplay of early exposures and maternal viral infections. Emphasising vaccination's protective effects before and during pregnancy, the study advocates integrating vaccination into maternal health programs. Public health measures should promote immunisation and address socioeconomic inequalities to lower paediatric cancer risk, aligning with previous studies linking parental health behaviours to childhood cancer incidence.

A Systematic Review of the Attitudes, Beliefs, and Acceptance of the COVID-19 Vaccine in the Western and Eastern Hemispheres.

The availability of an effective vaccine does not equate to its use; its effectiveness primarily depends on vaccine acceptance by the targeted population. Despite the rapid development and widespread access to the COVID-19 vaccine, herd immunity is yet to be achieved, with vaccine hesitancy as a major barrier. This study sought to systematically assess the beliefs, attitudes, and acceptance towards COVID-19 vaccines, including factors contributing to vaccination hesitancy in the Eastern and Western Hemispheres. A comprehensive search of articles was conducted through Scopus, PubMed, Embase, CINAHL, Cochrane CENTRAL, and Web of Science databases for studies published from inception to May 2023 using the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Our search yielded 1154, of which 21 were eligible for inclusion. The rate of willingness or intention to vaccinate varied with the geographic region, from 12% in the United States to 93.9% in China. Four studies from the Western region and two from the Eastern region reported a low acceptance rate (defined as <50%): United States (12%), Spain (48.3%), Switzerland (38.6%), Europe (multi-national, 31%), Nepal (38.3%), and Oman (43%). Overall, vaccine acceptance was low to moderate in the general population and healthcare workers (HCWs) in both Eastern and Western Hemispheres except for China which reported high acceptance (defined as >75%) among the general population and HCWs. Demographic characteristics (female, younger age, and higher education) and non-demographic factors (knowledge about the COVID-19 vaccine and its development, history of influenza vaccination, perceived susceptibility or severity of infection, and the belief that vaccines are effective in controlling the pandemic) were associated with high acceptance rates or intentions to take the COVID-19 vaccine. On the other hand, mistrust of the vaccine, its safety and effectiveness, disinformation or poor awareness of the vaccine, side effect concerns, belief in natural immunity, previous adverse experience with the vaccines, and distrust in the information sources about the COVID-19 pandemic were associated with vaccination hesitancy. For better acceptance, COVID-19 vaccination campaign strategies should be modeled based on regional political, economic, and social contexts.

Orthoflavivirus circulation in South-East Queensland, Australia, before and during the 2021–2022 incursion of Japanese encephalitis virus assessed through sero-epidemiological survey of a sentinel equine population

An incursion and outbreak of Japanese encephalitis virus (JEV) was reported in Australia in 2021 and 2022, respectively. There was speculation that JEV may have been circulating in Australia unknowingly prior to the detection. In this study, we determined sero-prevalence and transmission of West Nile virus (WNV), Murray Valley encephalitis virus (MVEV) and JEV, prior to and post JEV incursion in a sentinel equine population in south-east Queensland (SEQ), Australia, using blocking ELISAs (screening test) and virus neutralisation test (confirmatory). Serum samples collected between 2018 and 2020 (prior to JEV incursion; n = 607) from horses residing in SEQ revealed that sero-prevalence to pathogenic orthoflaviviruses was low, specifically WNV (1.3 %; 8/607), MVEV (1.2 %; 7/607), and JEV (4.9 %; 30/607). The significantly higher prevalence of JEV (P < 0.05) was skewed by the high proportion of horses previously enrolled in one or more JEV vaccine studies (17/30; 56.7 %) and the unknown JEV vaccination history due to international travel (6/30; 20 %). Thirty-two foals were enrolled as sentinels to monitor for arbovirus transmissions in SEQ between 2020 and 2023. Results showed that JEV seroconversion was first detected in April 2022 (n = 4), with seven more seroconversions detected in the following months until November 2022. This study (i) confirms that it is highly unlikely that JEV incursion in SEQ occurred prior to February 2022; (ii) circulation of WNV in SEQ remains very low; and (iii) highlights the complexity in the interpretation of orthoflavivirus serological results. The authors propose that horses should be included as sentinels for arbovirus transmission monitoring in Australia.

Serum microRNA 143 and 223 Gene Expression Profiles as Potential Biomarkers in Individuals with Hepatitis and COVID-19.

MicroRNAs (miRNAs) can act as biomarkers and descriptors of the association between infections and other diseases, such as hepatitis and COVID-19. This study aims to investigate the role of miRNA serum expression according to laboratory data concerning hepatitis and COVID-19. Seventy individuals recruited in Southern and Southeastern Brazil donated serum samples and were divided into four groups: (i) 20 negative subjects, (ii) 20 presenting hepatitis, (iii) 19 with COVID-19 and (iv) 11 with hepatitis and COVID-19. Three miRNAs (miR-122, miR-143 and miR-223) were evaluated using real-time PCR. Hematological and biochemical markers were also analyzed. MiR-143 and miR-223 were downregulated among the hepatitis/COVID-19 group (p < 0.05). A positive correlation was observed between miR-223 and lymphocytes. There was a negative correlation between alanine transaminase (ALT) and aspartate transaminase (AST) for miR-143 and miR-223 and gamma-glutamyl transferase (GGT), alkaline phosphatase (AP) and neutrophil/lymphocyte ratio (NLR) only for miR-223 (p < 0.05). For hepatic fibrosis (FIB-4), miR-122 and miR-143 had a greater association and miR-223 was more associated with a history of vaccination against COVID-19. MicroRNAs 143 and 223 could be useful as biomarkers for hepatitis coinfection with COVID-19.

Estimated Effectiveness of Influenza Vaccines in Preventing Secondary Infections in Households

Influenza vaccine effectiveness (VE) is commonly assessed against prevention of illness that requires medical attention. Few studies have evaluated VE against secondary influenza infections. To determine the estimated effectiveness of influenza vaccines in preventing secondary infections after influenza was introduced into households. During 3 consecutive influenza seasons (2017-2020), primary cases (the first household members with laboratory-confirmed influenza) and their household contacts in Tennessee and Wisconsin were enrolled into a prospective case-ascertained household transmission cohort study. Participants collected daily symptom diaries and nasal swabs for up to 7 days. Data were analyzed from September 2022 to February 2024. Vaccination history, self-reported and verified through review of medical and registry records. Specimens were tested using reverse transcription-polymerase chain reaction to determine influenza infection. Longitudinal chain binomial models were used to estimate secondary infection risk and the effectiveness of influenza vaccines in preventing infection among household contacts overall and by virus type and subtype and/or lineage. The analysis included 699 primary cases and 1581 household contacts. The median (IQR) age of the primary cases was 13 (7-38) years, 381 (54.5%) were female, 60 (8.6%) were Hispanic, 46 (6.6%) were non-Hispanic Black, 553 (79.1%) were Non-Hispanic White, and 343 (49.1%) were vaccinated. Among household contacts, the median age was 31 (10-41) years, 833 (52.7%) were female, 116 (7.3%) were Hispanic, 78 (4.9%) were non-Hispanic Black, 1283 (81.2%) were non-Hispanic White, 792 (50.1%) were vaccinated, and 356 (22.5%) had laboratory-confirmed influenza during follow-up. The overall secondary infection risk of influenza among household contacts was 18.8% (95% CI, 15.9% to 22.0%). The risk was highest among children and was 20.3% (95% CI, 16.4% to 24.9%) for influenza A and 15.9% (95% CI, 11.8% to 21.0%) for influenza B. The overall estimated VE for preventing secondary infections among unvaccinated household contacts was 21.0% (95% CI, 1.4% to 36.7%) and varied by type; estimated VE against influenza A was 5.0% (95% CI, -22.3% to 26.3%) and 56.4% (95% CI, 30.1% to 72.8%) against influenza B. After influenza was introduced into households, the risk of secondary influenza among unvaccinated household contacts was approximately 15% to 20%, and highest among children. Estimated VE varied by influenza type, with demonstrated protection against influenza B virus infection.

Clinical Features of Patients with COVID-19 Recurrence During Hospitalization in the Omicron Variant Surge.

Repeat positive results for SARS-CoV-2 by antigen detection test/RT-PCR in recovered COVID-19 patients were not very rare even when omicron variants became dominant, but the clinical features of patients with recurrent COVID-19 during hospitalization are still unclear. The clinical characteristics of patients with recurrent COVID-19 during hospitalization were retrospectively investigated from January 2023 to December 2023. Recurrence of COVID-19 was found in 7 of 275 (2.5%) patients during hospitalization. Their mean age was 80.3 (74-89) years, and 4 of 7 (57.1%) patients were hospitalized on the hematology ward with B cell/non-Hodgkin lymphoma. These 4 lymphoma patients had been vaccinated, but the other 3 patients hospitalized on the emergency ward and the neurology ward had not been vaccinated. Of the 7 patients, 6 (85.7%) were initially treated with remdesivir (RDV), but only 3 patients were re-treated with RDV, and the other 4 patients were successfully re-treated with oral 3C-like protease inhibitors, such as ensitrelvir (ESV) and nirmatrelvir/ritonavir (N/R). These data suggest that COVID-19 recurrence was found in patients with hematological disorders, such as lymphoma, and/or patients with no vaccination history. However, these patients were treated successfully by re-administration of anti-SARS-CoV-2 agents, including ESV and N/R.