Estimated size of the population at risk of severe adverse events after smallpox vaccination in Israel

Reintroducing OPV in Israel on the journey to global polio eradication - Estimation at a low rate of contraindicated population

INTRODUCTION

The 2013 reemergence of wild poliovirus in Israel led to the reinstatement of a routine OPV vaccination. Fearing VAPP in immunocompromised, the MOH regulated contraindications for vaccination candidates and household contacts. In this study we estimate the size of the contraindicated population to OPV vaccination.

METHOD

We studied vaccination candidates aged 2-9 and 14-23 months and probable household contacts. Using the rate of contraindications extracted for each study group from a medical records database, a statistical model was built to estimate the probability of contraindications in candidates.

RESULTS

3.9% of the 2-9-month-old study group and 4% of the 14-23-month-old group had contraindications by either self or household contacts.

CONCLUSION

A statistical model can provide an estimation of the contraindicated population and can be used in the future when devising vaccination campaigns. In contrast to concerns raised by the MOH, our findings show a smaller than anticipated contraindicated population.

Estimating the Size of the U.S. Population at Risk of Severe Adverse Events from Replicating Smallpox Vaccine

OBJECTIVE

To quantify the population at risk of serious adverse reactions to replicating smallpox vaccine.

DESIGN AND SAMPLE

Conditions known or suspected to carry risk were identified via Centers for Disease Control and Prevention planning documents, other federal publications, and peer-reviewed literature. Conditions identified were categorized as historically recognized risks or more recently recognized immunocompromised states that may pose risk. Major historical risk factors were as follows: eczema/atopic dermatitis, pregnancy, HIV, and primary immunodeficiency. More recently identified states were as follows: rheumatoid arthritis, inflammatory bowel disease, dialysis, bone marrow transplant recipients within 24 months post-transplant, solid-organ transplant recipients within 3 months post-transplant, age under 1 year, and systemic lupus erythematosus.

MEASURES

The estimated prevalence or absolute number of affected individuals for each condition was ascertained from peer-reviewed studies, vital statistics, and registry databases.

RESULTS

An estimated 48,121,280 to 50,028,045 individuals (15.2-15.8% of the U.S. population) are potentially contraindicated to replicating smallpox vaccine. This rises to 119,244,531 to 123,669,327 (37.4-38.8%) if household contacts are included.

CONCLUSIONS

These figures are significant and larger than the only previously published study. Understanding this number allows for improved clinical utilization, equitable attention to the health needs of a vulnerable population, and strategic vaccine stockpiling.