New research has found that a reduced dose of a Pfizer COVID-19 booster vaccine can elicit a comparable immune response in adults compared to a full dose with fewer side effects. The study, conducted by the Murdoch Institute and the National Centre for Communicable Diseases in Mongolia, is the first to assess and compare widely used COVID-19 vaccines in low- and middle-income countries. It involved 601 participants over 18 years old from Mongolia who had previously received AstraZeneca or Sinopharm COVID-19 shots.
The study found that reduced doses of the Pfizer booster produced a non-inferior immune response and may improve COVID-19 booster acceptability and uptake and reduce the per-dose cost of COVID-19 booster programs. This data can be used by policymakers and immunization advisory committees to make flexible boosting schedules decisions.
Participants receiving half doses reported fewer side effects compared to those receiving full doses, highlighting the potential benefits of this approach. Among half-dose boosted participants, 60 percent reported local reactions including pain and tenderness, and 25 percent reported systemic reactions including fevers, vomiting, diarrhea, and headaches. On the other hand, 72 percent of full-dose boosted participants reported local reactions, and 32 percent reported systemic reactions.
Amid these findings, recommendations from the Food and Drug Administration’s (FDA) vaccine adviser Dr. Paul Offit suggest that most people do not need another COVID-19 booster. The study has also noted that half-dose boosting may be less effective in adults primed with the Russian COVID-19 vaccine, Sputnik V.
The new research, published in the Lancet, is part of an international clinical trial funded by the Coalition for Epidemic Preparedness Innovations (CEPI), involving 3,300 healthy adults across Australia, Indonesia, and Mongolia, to investigate the impact of administering a reduced dose of COVID-19 booster shots. CEPI receives funding from the Australian government.