Protection against the omicron variant in individuals who received two doses of Coronavac increased up to seven-fold after receiving the Pfizer vaccine booster, a new study by Brazilian researchers shows, not yet peer-reviewed.
From December to March, period of entry and greater circulation of the new variant in Brazil, individuals who received two doses of Coronavac had only 8.1% protection against symptomatic Covid, the research indicates.
When receiving a third dose of Coronavac (the so-called homologous regimen, as it uses the same vaccine in the stages), protection rose to only 15%, while the booster with Pfizer (heterologous regimen, with different vaccines) offered protection of 56.7 % against developing symptoms of Covid.
As for the severe forms of the disease, the two doses of Coronavac offered protection of 57.3%. A Coronavac boost also increased this protection to 71.3%, while the Pfizer booster increased the protection to 85.5%.
These are the main results of the new study that evaluated the effectiveness (effectiveness in real life) of Coronavac and the booster with the same immunizer or that of Pfizer against the delta and ômicron variants. The pre-print of the study, still without review, was released on the medRxiv platform last Friday (1st).
The research, coordinated by Julio Croda, an infectologist and researcher at Fiocruz, is the first to assess the effectiveness of these immunizers and vaccine boosters in the context of two more transmissible variants of concern that have been proven in studies to reduce vaccine immunity. .
To assess the effectiveness of immunizers, scientists analyzed more than 1.3 million tests of the antigen or RT-PCR type with positive results from September 2021 to March 2022 throughout Brazil and compared with the same number of tests with positive results. negative.
The effectiveness of the omicron vaccines was analyzed from December 25, 2021 to March 10, 2022. It was compared with the protection against delta, from September 6 to December 14, 2021.
The arrival of the omicron resulted in a significant decrease in the effectiveness of vaccines worldwide, both against the symptomatic form of the disease and to protect against hospitalization and death.
In the case of individuals who received two doses of Coronavac, without vaccine booster, protection against the development of Covid symptoms was less than 10% in the omicron period; such protection was around 36% in the months of circulation of the delta variant.
With the reinforcement of Coronavac, protection against symptomatic Covid by the ômicron variant did not show a significant increase – about 7% -, but against severe forms, hospitalization and death, there was a moderate increase in protection from 8 to 59 days after the third dose, from 57% to 71.3%.
Regarding the booster with Pfizer, an extra dose in the delta period increased protection from 51% against Covid symptoms to 86.6%. Against hospitalization and death, the increase was from 86.7% to 91.7% from 8 to 59 days after the third dose.
According to Croda, the study is important because it is the first to assess the effectiveness of boosters in individuals vaccinated with Coronavac against the micron.
“For the delta variant, there is somehow an increase in protection [com o reforço de Coronavac] both for symptomatic disease and for hospitalization, that is, there is a benefit, but in the context of the Ômicron, this benefit is very marginal”, he says.
For Croda, the research data may help in the evaluation of public measures not only in the country, since Coronavac is also used in other countries, such as Chile and in China itself, where it was developed.
The researcher recalls that the article is still awaiting peer review and is being evaluated in a prestigious international journal, but that the knowledge produced can even be used to guide the decision to reinforce with the fourth dose.
At the conclusion of the study, the authors state that the findings reinforce research that already indicated greater protection of the heterologous booster regimen and the need for future analyzes comparing the effectiveness with other combinations of immunizing agents.
THE sheetPfizer said it does not comment on results of studies that were not conducted by the lab itself.
In a note, the Butantan Institute, responsible for Coronavac in Brazil, said that the study by Croda and colleagues showed a reduction in the effectiveness of Coronavac for Ômicron in general, a drop also observed for other vaccines.
“Even with a drop in effectiveness of the homologous scheme, it still showed high effectiveness, reaching 71.3% against severe Covid. It is important to note that these drops in effectiveness occur over time with all immunizers and that no vaccine prevents the infection, but serious cases and deaths”, says the institution.
In a note, Butantan also highlights that other studies have demonstrated the efficacy, safety and immunogenicity (ability to generate an immune response) of Coronavac in several parts of the world, including Brazil, in contexts with and without the ômicron variant.
The Ministry of Health announced, on March 23, the recommendation of the fourth dose against Covid for people aged 80 and over. According to the folder, as well as for the third dose, the orientation is that the second booster is preferably done with Pfizer and, alternatively, with the AstraZeneca and Janssen vaccines.
In the state of São Paulo, on the other hand, the PEI (State Immunization Program) determined that the booster with the fourth dose should be done with any immunizer that is available, including Coronavac.
In a note, the São Paulo State Health Department states that the “priority of the SP government has always been and will always be to protect and save lives” and that “the immunizers available in the public network can be used in the booster vaccine strategy in accordance with the guidelines of the PEI”.
“Coronavac received authorization from Anvisa [Agência Nacional de Vigilância Sanitária] for the immunization of the population, as well as the other immunizers used in the country, proving that they are safe, effective and have the same purpose: to protect against the disease and reduce the risks of serious infections by the coronavirus. The government defends the use of Coronavac and all immunizers”, says the folder.
For Croda, the decision of the state of São Paulo “goes against a recommendation [do Ministério da Saúde] which has a technical basis. “It doesn’t make sense for São Paulo to insist on this. And considering that any immunizing agent causes a smaller response [no sentido de efetividade] in the elderly, the difference with the booster dose of Coronavac in this group was even more pronounced”, he says.
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