Third dose of Pfizer vaccine protects against Omicron, studies show

Analyzes prove that booster is effective among those who took the first two doses from the same manufacturer and among those who received CoronaVac

Welcome to Velasco/EFEThird dose of Pfizer is effective against Omicron, study proves

The third dose of the vaccine pfizer Against the Covid-19 offers protection against the Ômicron variant, both in cases where the first two applications were hers or CoronaVac’s. The conclusion is from two studies published this week in the journal Nature Medicine that looked at the antibody response to infection in vaccinated and post-vaccinated people. The first, conducted by researchers at the University of Hong Kong on 30 people with a mean age of 48.9 years, looked at differences in antibody responses to the original infection or the Ômicron variant. The study included people uninfected one month after the second dose of Pfizer vaccine (31 participants; mean age 51.7 years) or CoronaVac (30 participants; mean age 52.1 years), and people who received three doses. CoronaVac (30 participants; mean age 50.5 years) or three doses of Pfizer (25 participants; mean age 50.6 years).

They found that two doses of either Pfizer or CoronaVac vaccine provided little neutralizing antibody immunity against Omicron infection, even one month after vaccination. However, when these two doses of either vaccine were supplemented with a booster dose from Pfizer, this new dose provided acceptable immunity (defined as antibody levels sufficient to provide greater than 50% protection against coronavirus) one month after vaccination. administration. They also found that three doses of Pfizer’s vaccine resulted in average levels of antibodies to Omicron one-third higher than those obtained with two doses of CoronaVac plus one of Pfizer, while three doses of CoronaVac did not generate sufficient neutralizing antibodies to Omicron.

In a second study, Akiko Iwasaki, a researcher at Yale University in Connecticut (USA) analyzed the effectiveness of a vaccination schedule followed by 101 people (70% of them women with an average age of 40.4 years) in the Dominican Republic. These people received two doses of CoronaVac and, at least four weeks later, a booster dose of Pfizer’s vaccine against the Delta and Omicron variants. Participants who received the mixture had elevated levels of virus-specific antibodies and strong neutralizing antibody responses against the parent virus and the Delta variant, compared to levels before boosting with the Pfizer vaccine. Although Omicron neutralization could not be detected in those who had only received two doses of CoronaVac, the Pfizer booster dose raised Omicron antibody levels 1.4-fold. However, despite this increase, the levels of neutralizing antibodies to the omicron were reduced globally by 7.1 and 3.6 times, in relation to the levels of antibodies to the original virus or to the Delta variant, respectively. The study noted that previous infection with the Sars-CoV-2 coronavirus did not significantly elevate levels of antibodies to omicron in participants who had received the mixed vaccine regimen. The authors concluded that these findings highlight the ability of the Omicron variant to evade vaccine-induced immunity or infection, and underscore the general importance of booster vaccines in efforts to combat emerging variants.

*With information from EFE

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