Pfizer and BioNTech said on Thursday that data from an advanced-stage trial demonstrated the high efficacy of a booster dose of their COVID-19 vaccine, including against the Delta variant of the novel coronavirus.
They said that a trial of 10,000 participants of 16 years aged and over showed 95.6% efficacy against the disease during a period when the Delta strain was prevalent. The study also found that the booster dose exhibited a favorable safety profile.
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Pfizer had said that the effectiveness of its two-dose vaccine decreases over time, citing a study that showed 84% effectiveness four months after a second dose — the peak is 96%. In Latin America, Brazil, Colombia, and Chile are already inoculating booster doses for the elderly and immunosuppressed people.
The drugmakers said the median time between the second dose and a booster dose or a placebo in the study was about 11 months, adding that there were only five cases of COVID-19 in the booster group and 109 cases in the placebo group. “These results provide further evidence of the benefits of boosters as we aim to keep people well-protected against this disease,” Pfizer Chief Executive Albert Bourla said in a statement.
The study’s results will submit detailed study results to publications in the scientific community, the US Food and Drug Administration (FDA), the European Medicines Agency (EMA), and other regulatory agencies as soon as possible.
Chile’s good experience
In early October, health authorities in Chile, the country that led vaccination in Latin America, released a study on the response generated by the third dose. 2,017,878 vaccinated with CoronaVac in the country received a booster dose.
In detail 1,506,154 of them received AstraZeneca; 371,592, Pfizer-BioNTech, and 140,132 CoronaVac. The main conclusion is that all vaccines used as booster doses can significantly increase the levels of effectiveness to prevent symptomatic COVID-19.
In the case of CoronaVac, it far exceeded estimates with two doses, increasing its effectiveness from 56% to 80.2%. With Pfizer-BioNTech, it rose from 56% to 90%, and with AstraZeneca, from 56% to 93%.
