Summary of Findings and Rationale for Recommendations
For the first and second questions, regarding recommendation for JYNNEOS as an alternative to ACAM2000 for primary vaccination, the systematic review identified three randomized controlled studies and 15 observational studies including a total of 5,775 subjects. After considering geometric mean titers and seroconversion data together, the Work Group had moderate (level 2) certainty that JYNNEOS provides a small increase in disease prevention compared with that provided by ACAM2000.† The Work Group estimated with low (level 3) certainty that fewer serious adverse events occur following the JYNNEOS primary series compared with ACAM2000 primary vaccination, and that fewer events of myopericarditis occur after JYNNEOS primary series than after ACAM2000 primary vaccination. Based on the results from the GRADE assessment and EtR framework,§ ACIP unanimously voted in favor of the JYNNEOS vaccine as an alternative to ACAM2000 for primary vaccination.
To address the third and fourth questions, regarding booster doses, the systematic review identified one randomized controlled trial and 17 observational studies that included a total of 6,417 subjects. After considering geometric mean titer and seroconversion rate together, the Work Group estimated with very low (level 4) certainty that a small increase in disease prevention occurs after JYNNEOS booster versus the JYNNEOS primary series only.¶ The Work Group estimated with very low (level 4) certainty that fewer serious adverse events occur after a JYNNEOS booster administered following completion of the JYNNEOS primary series compared with the JYNNEOS primary series (i.e., no booster dose). No myopericarditis events were recorded in either the intervention or comparison; for this reason, the effect was not estimable and the Work Group had very low (level 4) certainty that myopericarditis does not occur after JYNNEOS boosters because of inadequate sample size to detect rare events. The ACIP unanimously voted in favor of the JYNNEOS booster vaccine after the 2-dose JYNNEOS primary series. ACIP recommended that the JYNNEOS booster dose be administered every 2 years to persons working with more virulent orthopoxviruses and every 10 years to persons working with less virulent orthopoxviruses.
For the fifth question, regarding providing the option of transitioning to JYNNEOS for a booster dose in persons who had received primary vaccination with ACAM2000, the systematic review identified one randomized controlled trial and five observational studies that included a total of 435 subjects. A total of 82% of subjects seroconverted when given JYNNEOS booster, with very low (level 4) certainty in that estimate. The Work Group estimated, with low (level 3) certainty, fewer serious adverse events occurred after the JYNNEOS booster than after the ACAM2000 booster in persons previously vaccinated with ACAM2000** and that fewer myopericarditis events occurred after a JYNNEOS booster than after an ACAM2000 booster in persons who received ACAM2000 as the primary vaccine (very low [level 3] certainty). Based on the results from the GRADE methodology and findings within the EtR framework,†† ACIP unanimously voted in favor of recommending JYNNEOS boosters as an alternative to ACAM2000 boosters in persons who received ACAM2000 as the primary vaccine.
Morbidity and Mortality Weekly Report. 2022;71(22):734-742. © 2022 Centers for Disease Control and Prevention (CDC)