Covid: Fiocruz and Sabin test the effectiveness of fractional dose booster

Fundação Oswaldo Cruz do Mato Grosso do Sul (Fiocruz) and Instituto Sabin de Vacinas started a study to evaluate the possibility of splitting booster doses of vaccines against Covid-19.

The researchers want to understand whether lower doses can offer the same immune response to the body, with fewer adverse reactions.

Positive results would enable a greater supply of vaccines to the population, facilitating access in low- and middle-income countries.


The study will be carried out with 1,440 Brazilian volunteers who have not yet taken booster doses. They will be followed up for six months after receiving vaccines from Pfizer – full, half or one third dose –, AstraZeneca – full or half dose – or Coronavac – full dose.

During this period the researchers will make four visits within 28 days after the application of the immunizer, three months and six months to collect blood samples from the participants.

“With the pandemic, there was great pressure for an immunizing agent that was effective. We were in a situation where we couldn’t risk failing. But we’re at a point now where we have the opportunity to optimize that dose,” said Vice President of Applied Epidemiology at the Sabin Vaccine Institute, Denise Garrett.

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