Varicella seroepidemiology and immunization in a cohort of future healthcare workers in the pre-vaccination era

Maternal varicella antibodies in children aged less than one year: Assessment of antibody decay

OBJECTIVES

To investigate maternal antibody levels to varicella in infants <12 months of age in Ontario, Canada.

STUDY DESIGN

In this study, we included specimens from infants <12 months of age, born at ≥37 weeks gestational age, who had sera collected at The Hospital for Sick Children (Toronto, Canada) between 2014-2016. We tested sera using a glycoprotein-based enzyme-linked immunosorbent assay (gpELISA). We measured varicella susceptibility (antibody concentration <150mIU/mL) and mean varicella antibody concentration, and assessed the probability of susceptibility and concentration between one and 11 months of age using multivariable logistic regression and Poisson regression.

RESULTS

We found that 32% of 196 included specimens represented infants susceptible to varicella at one month of age, increasing to nearly 80% at three months of age. At six months of age, all infants were susceptible to varicella and the predicted mean varicella antibody concentration declined to 62 mIU/mL (95% confidence interval 40, 84), well below the threshold of protection.

CONCLUSIONS

We found that varicella maternal antibody levels wane rapidly in infants, leaving most infants susceptible by four months of age. Our findings have implications for the timing of first dose of varicella-containing vaccine, infection control measures, and infant post-exposure prophylaxis recommendations.

Prevalence of healthcare workers fully vaccinated against hepatitis B without circulating antibodies in Italy and role of age at baseline cycle vaccination: a systematic review and meta-analysis

INTRODUCTION

Healthcare workers (HCWs) susceptible to hepatitis B represent an important public health concern. National and international guidelines recommend assessing the hepatitis B immune status of all HCWs and possibly vaccinating those found to be seronegative (non-responders). We conducted a meta-analysis to estimate the rate of hepatitis B sero-susceptibility among HCWs in Italy and to explore possible options for the management of non-responders.

AREAS COVERED

Nineteen studies, selected from scientific articles available in the Scopus, MEDLINE/PubMed and ISI Web of Knowledge databases between 1 January 2016 and 22 April 2022, were included. The prevalence of HBV-susceptible HCWs was 27.1% (95%CI = 23.2-31.7%). In a comparison by sex (males vs. females) the RR was 1.16 (95%CI = 1.03-1.31), and by full-cycle vaccination period (adolescence vs. infancy) the RR was 0.30 (95%CI = 0.25-0.37). Occupational health screenings for hepatitis B, with subsequent vaccination of non-responders, and exclusion of susceptible HCWs from high-risk settings have been common management strategies.

EXPERT OPINION

It is highly probable that a proportion of the next generation of medical students and HCWs will not show circulating IgG on serologic evaluation. Therefore, more targeted efforts are needed to identify these individuals and actively immunize them.

Vaccination Offer during the Occupational Health Surveillance Program for Healthcare Workers and Suitability to Work: An Italian Retrospective Cohort Study

The active immunization of health care workers (HCWs) is a crucial measure to avoid nosocomial infection; nevertheless, vaccine coverage (VC) among health personnel in Italy is unsatisfactory. To improve VC in the healthcare set, the Hygiene and Occupational Medicine departments of Bari Policlinico General University Hospital applied a specific program. The operative procedure demands that in the context of the occupational medical examination, all workers are evaluated for susceptibility to vaccine-preventable diseases (VDPs), with immunization prophylaxis offered to those determined to be susceptible. This study analyzed data from workers who attended the biological risk assessment protocol from December 2017 to October 2021 (n = 1477), who were evaluated for the immune status for measles, mumps, rubella, and varicella. Among the enrolled subjects, non-protective antibody titers were higher for measles and mumps (13%), followed by rubella (11%) and varicella (8%). Appropriate vaccinations were offered to all susceptible HCWs, and HCWs were re-tested one month after immunization. The seroconversion rate after the administration of one or more booster dose(s) was over 80%. Overall, 2.5% of the subjects refused the offered vaccine(s); the main determinant of immunization compliance was younger age (aOR = 0.86; 95%CI = 0.80–0.92). Especially during the COVID-19 pandemic, VPDs may still present a hazard in nosocomial environment. Our experience suggests that, despite hospital procedures and dedicated human assets, satisfactory VC cannot be reached without the provision of federal regulations. Nevertheless, public health policymakers have to improve the promotion of vaccine prophylaxis and education to reach higher VC.

Uptake of Non-Mandatory Vaccinations in Future Physicians in Italy

In 2017 in Italy, a number of vaccinations became mandatory or started to be recommended and offered free of charge. In this study, we aimed at assessing the coverage rates for those vaccinations in the pre-mandatory era among students at the School of Medicine of Padua University studying the degree course in medicine and surgery (future physicians) on the basis of the vaccination certificates presented during health surveillance. The vaccinations considered were those against pertussis, rubella, mumps, measles, varicella, Haemophilus influenzae type b (which became mandatory in 2017), pneumococcus, meningococcus C and meningococcus B (only suggested and offered for free since 2017). The study enrolled 4706 students of medicine and surgery. High vaccine uptake was observed, especially in younger students (born after 1990), with vaccines against pertussis, rubella, mumps and measles. Good completion for Haemophilus influenzae type b and meningococcus C was also observed. Very low coverage rates (all under 10%) for vaccination against varicella, pneumococcus and meningococcus B were observed. In conclusion, uptake for some non-mandatory vaccines was below the recommended threshold, although younger generations showed a higher uptake, possibly as a results of policy implemented at the national level. Our findings support the idea to consider health surveillance visits also as an additional opportunity to overcome confidence and convenience barriers and offer vaccine administration.

Rubella Serosurvey Among Future Healthcare Workers

Objective: Rubella is a very diffusive but relatively benign infectious disease unless contracted during pregnancy, when it causes congenital rubella syndrome. The aim of this research was to determine the prevalence and titer of antirubella antibodies in a population of future healthcare workers (students at the school of medicine). Methods: The cohort consisted of 11,022 students who underwent antibody analysis after the presentation of a vaccine certificate. Results: Vaccination compliance was very high, particularly in younger students (born after 1995), reaching almost 100% (at least one dose). Unvaccinated students born before 1990 had high seropositivity (>95%), but this percentage dropped to zero among the youngest students. Variables affecting antibody titer included year of birth and sex. Considering only vaccinated students, a greater antibody response was observed if the vaccine was administered between 8 and 10 years of age. Female sex was associated with more significant (p < 0.0001) positivity and higher antibody titer after one and two doses. However, this difference appeared less consistent in relation to year of birth. Conclusions: The studied population exhibited excellent vaccination compliance, high seropositivity, and high antibody titer. Vaccine and immune coverage were higher than what is deemed necessary to achieve herd immunity.

Response to Vaccination against Mumps in Medical Students: Two Doses Are Needed

Mumps is a vaccine-preventable infectious disease diffuse worldwide. The implementation of mumps vaccination reduced largely the spread of infection. On 11,327 Medical School students the prevalence of mumps positive antibodies was evaluated according to dose/doses of vaccine, year of birth and sex. Compliance to mumps vaccine was low in students born before 1990 but increased consistently after this year, above all compliance to two doses, due to the implementation of the vaccine offer. Positivity of mumps antibodies is significantly (p < 0.0001) lower in students vaccinated once (71.2%) compared to those vaccinated twice (85.4%). In addition, students born after 1995, largely vaccinated twice, showed a seropositivity near to 90%. Further, females had a significantly (p < 0.0001) higher proportion of positive antibodies after vaccination than males, both one (74.6% vs. 64.7%) and two doses (86.8% vs. 82.9%). Finally, seropositivity after two vaccine doses remains high (86.1%) even 15 years after the second dose. In conclusion, the research highlighted that vaccination against mumps reaches a good level of coverage only after two doses of vaccine persisting at high levels over 15 years and induces a more significant response in females.

Long -term persistence of antibodies against varicella in fully immunized healthcare workers: an Italian retrospective cohort study

Background

Chickenpox is a highly contagious disease caused by the varicella zoster virus (VZV), and in infants, adolescents, adults, pregnant women, and the immunocompromised it can be serious. The best way to prevent chickenpox is immunization with the varicella vaccine. Protective levels of antibodies induced by the varicella vaccine decline over time, but there is currently no formal recommendation for testing anti-varicella zoster virus (VZV) IgG levels in immunized healthcare workers (HCWs).

Methods

The aims of this study were to evaluate the seroprevalence of circulating anti-VZV IgG in a sample a sample of students and residents of the medical school of the University of Bari, the long-term immunogenicity of the varicella vaccine, and the effectiveness of a strategy consisting of a third vaccine booster dose. The study population was screened as part of a biological risk assessment conducted between April 2014 and October 2020. A strategy for the management of non-responders was also examined.

Results

The 182 students and residents included in the study had a documented history of immunization (two doses of varicella vaccine). The absence of anti-VZV IgG was determined in 34% (62/182; 95%CI = 27.2–41.4%), with serosusceptibility more common among males than females (p < 0.05). After a third varicella dose, seroconversion was achieved in 100% of this previously seronegative group. No serious adverse events were recorded.

Conclusions

One-third of the study population immunized against VZV lacked a protective antibody titer, but a third dose of vaccine restored protection. Since it is highly unlikely that VZV will be eliminated in the immediate future, the loss of immunity in a substantial portion of the population implies a risk of varicella outbreaks in the coming years. Screening for varicella immunity in routine assessments of the biological risk of medical students and HCWs may help to prevent nosocomial VZV infections.