The COVID-19 vaccines made by Pfizer and Moderna are most effective at boosting antibody levels among fully vaccinated adults, according to a study published Dec. 2 in The Lancet.
The study, which took place in the U.K. over the summer, involved 2,878 adults ages 30 and older. Researchers analyzed the safety and efficacy of seven vaccines administered to participants after they received two initial doses of either AstraZeneca's vaccine or Pfizer's vaccine. The seven vaccines were produced by AstraZeneca, Pfizer, Novavax, Johnson & Johnson, Moderna, Valneva and Curevac.
Four key findings:
- All seven vaccines boosted immunity when administered 10 to 12 weeks after the second dose of AstraZeneca's vaccine.
- All vaccines except the one made by Valneva boosted immunity among participants whose two initial vaccines were made by Pfizer.
- The strongest immunity boost came from a half or full dose of Pfizer's vaccine or a full dose of Moderna's vaccine, regardless of whether participants were initially inoculated with AstraZeneca's or Pfizer's vaccine.
- No safety concerns were recorded among any of the vaccines. The most common side effects were fatigue, headaches and pain at the injection site.