Reducing the dose of a widely used COVID-19 booster vaccine produces a similar immune response in adults to a full-dose with fewer side effects, according to a new study.
The researchers found that a half dose of a Pfizer COVID-19 booster vaccine elicited a non-inferior immune response to a full dose in Mongolian adults who previously had AstraZeneca or Sinopharm COVID-19 shots.
But it found half-dose boosting may be less effective in adults primed with the Sputnik V COVID-19 vaccine.
The research is part of an international clinical trial, which also includes Australia and Indonesia, that’s investigating the different COVID-19 booster shot approaches to help guide future vaccination strategies.
The first batch of findings, involving 601 participants over 18 years old from Mongolia, reports on the initial responses seen 28 days after vaccination. The study is the first of its kind to assess and compare COVID-19 vaccines widely used in low- and middle-income countries.
MCRI Professor Kim Mulholland, who also sits on the WHO SAGE committee, said: “Fractional dosing may improve COVID-19 booster acceptability and uptake and reduce the per-dose cost of COVID-19 booster programmes.”
The study found half-dose boosted participants reported fewer local reactions than those receiving full doses (60% versus 72%) including less pain and tenderness. They also reported fewer systemic reactions (25% versus 32%).
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