Refrigerator-stable varicella vaccine held safe and effective

In a head-to-head study with frozen formulations of the vaccine, refrigerator-stable varicella vaccine had comparable safety, tolerability, and immunogenicity profiles when administered concomitantly with MMR vaccine, according to a study in Vaccine.

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In this double-blind, controlled, multicenter study, Keith S. Reisinger of Primary Physicians Research, Pittsburgh, and his colleagues randomized 958 subjects aged 12-23 months to receive either 8,000 plaque-forming units (PFU) refrigerated vaccine (n = 320; group 1), 25,000 PFU refrigerated vaccine (n = 315; group 2), or 10,000 PFU frozen vaccine (n = 323; group 3), and subjects in all three groups also received MMR vaccine. The primary endpoint for immunogenicity was percentage of subjects with at least 5 titers of varicella antibody according to glycoprotein enzyme-linked immunosorbent assay among the three groups 6 weeks post vaccination; the primary safety endpoint was incidences of vaccine-related adverse events during days 0-42 post vaccination.

The percentages of subjects meeting the primary endpoint for immunogenicity were comparable among the groups, at 93%, 94%, and 95% for groups 1, 2, and 3, respectively. Results for the safety endpoints also were similar among the groups; for example, rates of injection-site adverse events or vaccine-related injection-site adverse events were 44%, 40%, and 43%, with no statistically significant between-group differences.

The study authors noted that one of the problems with having only frozen formulations is how that limits availability in parts of the world where only refrigeration of 2°C–8°C is available. “Use of a refrigerator-stable formulation of varicella vaccine will allow for increased availability of the product throughout the world and may help to increase vaccination rates against varicella,” they concluded.

Strengths of the study included its head-to-head design. Limitations included how adverse events were based on parental reporting.

Some authors reported relationships, including employment, with Merck & Co, which developed the vaccine in this study and funded the study.

cpalmer@mdedge.com

SOURCE: Reisinger KS et al. Vaccine. 2018 Aug 23. doi: 10.1016/j.vaccine.2018.01.089.