According to a study released Tuesday by Brazil's Oswaldo Cruz Foundation (Fiocruz), patients who have taken the two-shot scheme of CoronaVac's drug would be better off if they receive a booster injection of the Pfizer vaccine.
The research evaluated data from e-SUS, the Influenza Epidemiological Surveillance Information System (Sivep-Gripe), and the National Immunization Program (PNI). The data cover from September 6, 2021, to March 10, 2022, and were divided into two periods, from September 6, 2021, to December 14, 2021, when the Delta variant was dominant in Brazil; and from December 25, 2021, to March 10, 2022, when there was a greater circulation of the Omicron variant.
To evaluate the effectiveness of the booster dose in people vaccinated with two doses of CoronaVac, three scenarios were designed. In the first, people who received two doses of the made-in-Brazil version of CoronaVac (produced at Sao Paulo's Butantan Institute and therefore known as ButanVac) and did not reinforce the immunization in the following six months were analyzed. The researchers calculated that the effectiveness of only doses against symptomatic infections during the period of greatest circulation of the Omicron variant was 8.1%, while protection against severe disease outcomes reached 57%.
The second scenario consisted of cases in which people received a booster dose of CoronaVac as well, which produced an amount of additional protection that was considered limited. The effectiveness against symptomatic infections was 15%, and against severe cases, 71.3%.
The third scenario, in which the booster dose was with the Pfizer vaccine, showed the highest percentages of effectiveness: 56.8% against symptomatic infections and 85.5% against severe cases. In addition, the study showed that 90 days after the booster dose, protection against severe cases did not drop as was observed in the three-dose CoronaVac vaccination.
The researchers state that the findings reinforce the guidance of the Ministry of Health that the booster dose should be primarily with vaccines with messenger RNA technology. The recommendation was published in a technical note in November 2021.
In Brazil, Pfizer's drug is the only one with this technological platform. In other parts of the world, Moderna's vaccine shares the same principle. COVID-19 vaccines used in Brazil are from three different technology platforms. Besides Pfizer's, which contains synthetic RNA from SARS-CoV-2, there are also the viral vector vaccines (AstraZeneca and Janssen), in which another virus is used as a vector to carry genetic information from the coronavirus, and then there are those based on inactivated viruses (CoronaVac), which contains the dead virus, unable to replicate.
A similar study in France also yielded results pointing in the same direction. Researchers determined that Johnson & Johnson's vaccine was much less effective in preventing hospitalizations than the serum from Pfizer-BioNTech. The peer-reviewed study, published in the Journal of the American Medical Association (JAMA), surveyed 1.4 million people over the age of 55 in that country and concluded that the risk of being hospitalized with severe coronavirus after vaccination was about five times higher in people who received the J&J vaccine compared to the Pfizer-BioNTech injection.
The J&J vaccine is a single-dose treatment. Hence, researchers recommended that people who received it get a second booster dose with an mRNA vaccine such as Moderna and Pfizer. According to the published results, there were 129 coronavirus-related hospitalizations in participants vaccinated with J&J while there were only 23 hospitalizations in the case of those immunized with the Pfizer serum.
Pfizer's vaccine was 92% effective in preventing hospitalization with severe COVID-19, compared with 59% for the J&J vaccine, the researchers found, in agreement with previous estimates from smaller studies. The study is the largest to assess the effectiveness of the J&J vaccine in the general population to date and ”included almost the entire population (of France) aged 55 years or older” who received the vaccine.
The findings reinforce advice recommending that those who received the J&J vaccine receive a second booster dose with an mRNA vaccine, the technology used in the Moderna and Pfizer shots, the researchers said.
In clinical trials, J&J's vaccine had shown an 85% efficacy. In subsequent studies in the general population, this figure fell to around 68%, rendering J&J the worst-performing vaccine in the country. The number of people who have received the J&J vaccine in the U.S. stands at 17 million, according to CDC data, while more than 123 million have received two doses of Pfizer and more than 75 million have received two shots of Moderna.
Several foreigners traveled to the U.S. at the beginning of the pandemic when vaccines were not widely available and chose J&J because being a single-dose treatment they would not have to remain in the country for three weeks or return at a later date for the follow-up injection. Among them is former Argentine President Mauricio Macri.
(Sources: Agencia Brasil, El Cronista)