Preliminary study indicates Coronavac’s greater efficacy with longer intervals between doses

RIO DE JANEIRO, BRAZIL – A scientific paper in preprint (not yet peer-reviewed) points out that the efficacy of Coronavac against Covid-19 is higher than previously reported. The so-called primary efficacy, which represents the vaccine’s protection against the disease at any intensity, increased from 50.38% to 50.7%, reaching 62.3% with longer intervals between doses. Against moderate cases, the immunization is 83.7% effective, when the previous data indicated 78%.

The information is contained in an article prepared by the professionals who conducted the Coronavac tests in Brazil, led by the Butantan Institute. The document was submitted to the scientific journal The Lancet for analysis.

The study evaluated the effect of the vaccine in 12,400 volunteers in 16 research centers in the country and had the first results announced by the government of São Paulo on January 7. The vaccine began to be administered nationwide on January 18 and the production by Butantan represents most of the doses distributed so far.

“This study corroborates what we had already announced about three months ago and gives us even more security about the effective protection that the Butantan vaccine provides. There is no shadow of doubt about the quality of the immunizer,” said Dimas Covas, director of the Butantan Institute, in a statement to the press.

The analysis released this Sunday, April 11, points out that the results of efficacy can improve if there is a longer interval between doses. In the study, most of the volunteers were administered the vaccine with a 14-day interval given the urgency for analysis of the immunizer and the need for protection of health professionals.

The researchers believe that a 28-day period is most appropriate. “The data suggest that it is recommended to encourage longer intervals between doses, such as 28 days, in vaccine implementation,” they write in the article.

The Coronavac package insert stipulates the interval for the second dose as 14 to 28 days, but application from the 21st is already advocated by Butantan since January. A longer interval between doses was even considered as a way to extend the vaccination coverage and accelerate the application, but this option was not implemented. An interval longer than 28 days is not a consensus among experts because of the unstudied effects on the effectiveness of the immunizer.

Another piece of information in the article is that Coronavac has been shown to be effective in protecting against the so-called P.1 and P.2 variants of the SARS-CoV-2 virus. “Although the variants have several mutations that are key to the function of many antibodies, there was consistent neutralization of these variants by the serum of participants who received the inactivated vaccine,” the experts scored in the paper.

The increase in circulation of P.1, the so-called Brazilian variant, first identified in Manaus, is associated with the sharp rise in the curve of cases, hospitalizations and deaths seen in the country since January.