Risk of Covid-19 infection halved 13 days after 1st Pfizer/BioNTech dose – Israel study

RIO DE JANEIRO, BRAZIL – Between the 13th and 24th day after the first dose, the Pfizer/BioNTech Covid-19 vaccine reduces risk of infection by the novel coronavirus by 51.4%, according to a study conducted in Israel and published on Monday, June 7, in JAMA scientific journal (Journal of the American Medical Association). The efficacy for symptomatic Covid-19 cases is 54.4%.

Among the 3,098 confirmed Covid-19 cases in the sample analyzed, 2,484 occurred within the first 12 days, while 614 of positive RT-PCR tests occurred in the period between the 13th and 24th day. Respectively, the coronavirus incidence rate for each of the two periods stood at 12.07 and 6.16 – that is, for every 100,000 people, there were 43.41 infections in the first time frame and 21.08 in the second.

Thus, the researchers’ calculated efficacy for the American vaccine 13 days after the first dose is 51.4%. The study in Israel did not analyze the performance of the U.S. vaccine after the second dose.

For Raquel Stucchi, infectologist at the State University of Campinas (UNICAMP) and consultant for the Brazilian Society of Infectious Diseases (SBI), once a number of people are vaccinated with the first dose, there is considerable progress towards an “efficient control of the pandemic.” According to her, particularly is this the case of the first dose of the Pfizer/BioNTech vaccine, which offers protection similar to that conferred by two vaccine doses, such as the Coronavac, made by the Butantan Institute in partnership with Chinese Sinovac pharmaceutical company.

However, the infectious disease expert stresses that the population needs to remain aware of the need to take the second dose to further reduce the risk of infection by the novel coronavirus. “Despite this good first dose result, a second dose is required to ensure protection of around 90% efficacy [in the case of the Pfizer/BioNTech immunization],” says Stucchi.

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