Due to the increased number of cases caused by the spread of the Delta variant all over the world, global institutions are carrying out studies to verify the efficacy of immunizers against these variants. In a survey by Public Health England (PHE), data showed that the AstraZeneca vaccine, produced in Brazil by Fiocruz, is 92% effective against hospitalizations and severe cases caused by the Delta variant.

A new study coordinated by Oxford University in a partnership with the Organization for National Statistics (ONS) and with the Department of Health and Social Care (DHSC) of the UK analyzed more than 2.5 million tests made on 384,543 people above 18 years old, between December 1st 2020 and May 16th 2021, when the alpha variant was the main strain in circulation. Between May 17th and August 1st this year, when Delta was already the predominant variant, the research collected more than 810,000 tests.

The published analysis observed that the two doses of Pfizer and AstraZeneca provide the same level of protection as if the subjects had contracted the virus. The difference lies in the time it takes to lose effectiveness: the immunity provided by the AstraZeneca vaccine lasts longer. In the 18 to 64 age group, for example, Pfizer's effectiveness rate dropped by about 22% every 30 days after the second dose. With the AstraZeneca vaccine, this reduction was of only 7% in the same period.

There is no evidence that the effectiveness of both varies according to the interval of application between the doses, but the study suggests that protection is higher among those who have been vaccinated and who had been infected before. For example, 14 days after AstraZeneca's second dose, the effectiveness rate against infection was 88% in those who had already contracted the virus, versus 68% in those who had never had the disease; among those immunized with Pfizer, it was 93% and 85% respectively. For Pfizer, figures were 93% and 85%, respectively.

Effectiveness rates also change according to the age group. The Pfizer vaccine is 90% effective among people between 18 and 34 years old. The AstraZeneca vaccine is 73% effective in the younger group, against 54%.

It is necessary to emphasize that vaccines can reduce and eliminate the number of hospitalizations and of cases of the disease, but at this moment, a vaccinated person can still contract the virus and infect other people. This is why other prevention measures we have come to be familiar with are still necessary, such as hand sanitizer and masks.

With information from the Fiocruz News Agency