A woman in São Paulo is looking at the syringe that will be used to give a shot of Sinovac’s COVID-19 vaccine.
Other Pens / AP
By Sofia Moutinho
ScienceThe COVID-19 reporting is supported by the Heising-Simons Foundation.
As potentially more dangerous coronavirus variants spread worldwide, scientists and clinicians rushed to discover how well the available COVID-19 vaccines protect against the mutant strains. Preliminary results from a large study among health workers indicate that one dose of CoronaVac, a vaccine developed by a Chinese company, is still about 50% effective against symptomatic COVID-19 in a Brazilian city where more than three-quarters of the new cases occur. caused by the highly transmissible variant known as P.1.
Real-world protection is about the same as with two doses of CoronaVac against the standard, or ‘wild-type’, pandemic coronavirus in the country, which suggests that mutations in the variant do not have the capability of SARS-CoV-2 to evade vaccine increases -called immune responses.
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“This is very good news and supports the continued use of this vaccine in Brazil and other countries with the spread of the same variant,” said Julio Croda, a physician and researcher at the Oswaldo Cruz Foundation, who led the study. The protection of the vaccine may be even better after the second dose, he adds, noting that the study is ongoing.
Although 50% efficacy is far below the greater than 90% protection of COVID-19 vaccines with messenger RNA (mRNA), it may still be good enough to limit the spread of the disease in Brazil; vaccines with that effectiveness in a clinical trial, can use emergencies in many places and also meet the threshold of the World Health Organization.
It is also not clear how well the mRNA vaccines protect against the P.1 variant; their clinical trials took place before it spread or in places with little of the variant. In addition, CoronaVac is likely to offer much greater protection against serious illness, hospitalization, and death than against milder cases of COVID-19. It has been seen in two dose efficacy trials conducted in Brazil and other countries, and is typical of COVID-19 vaccines. But the new study has not yet collected enough serious cases to calculate effectiveness, Croda says.
The study’s preliminary results, which have not yet been reviewed by a peer, were posted on a pre-printed server yesterday and are the first to assess the effectiveness of the vaccine made by Sinovac Biotech in an area flooded with the P.1 variant. CoronaVac contains inactivated whole copies of SARS-CoV-2, unlike many other COVID-19 vaccines, including the mRNA vaccines, which provide only the protein of the virus to the immune system.
The origin of the P.1 variant was traced to Brazil in January, and the tension quickly spread to the rest of the world. Laboratory studies determining whether vaccine-induced antibody bodies can neutralize the infectivity of SARS-CoV-2 have raised concerns that the variant may escape immune protection through vaccines. The mutated virus is likely to cause a recent revival of COVID-19 in Brazil – the country currently has up to 60.00 new cases per day. COVID-19 killed more than 340,000 Brazilians.
The CoronaVac study included medical data from 67,718 health workers from Manaus, a city in the Amazon region that is at the center of the P.1 variant. The mutant virus is now responsible for 75% of all positive test results in the city, where the health system collapses due to COVID-19.
To estimate the effectiveness of CoronaVac, the researchers focused on 2656 healthcare professionals who started the initial deployment of the vaccine from January, with the initial introduction of the vaccine last week, with 2656 healthcare professionals contracting SRS-CoV-2 infections ( PCR). The scientists identified 786 people with COVID-19 symptoms, who divided them into two groups of 393 each: those who tested positive and negative for the virus. Thereafter, the researchers examined the percentage of vaccinated and non-vaccinated people in both groups. In the positive group, 18.6% were vaccinated; in the negative group, the share was 24.4%. Using the unvaccinated humans as a reference, the researchers calculated the risk of infection by SARS-CoV-2 14 days after the first dose.
The reality of 49.6% in the real world is similar to the efficacy of the vaccine of 50.34% against symptomatic COVID-19 after both doses. “This is not a coincidence,” said epidemiologist Ricardo Palácios, who conducted the vaccination tests at the institution, which now manufactures CoronaVac under an agreement with Sinovac. “This is an independent confirmation that the vaccine is effective in a scenario of a new variant.”
However, epidemiologist Eric Feigl-Ding at the Federation of American Scientists warns that the new study did not set up SARS-CoV-2 in people with positive PCR tests to make sure their infections were caused by the P.1 variant. The authors’ conclusion that the vaccine protects against the variant is based on the assumption that it constitutes the most positive cases, he notes.
On the other hand, says Feigl-Ding, measuring the effectiveness of the vaccine in Brazil can artificially produce low results because there is a high risk that humans have some immunity due to previous contact with the virus. . “It’s a natural trait to do a trial in a population that was very previously infected,” he says. This may also explain why the CoronaVac clinical trial in Brazil showed lower efficacy rates (50%) than in other countries such as Turkey (83.5%) and Indonesia (65%).
CoronaVac may appear to be better in a general population, as the data from the new trial come from health workers who are highly exposed to the virus, shows immunopathologist Bruno Filardi at the Brazil Cancer Institute. “The effectiveness is likely to be higher than the preliminary study shows,” he says. In addition to Brazil, CoronaVac is authorized and used in China, Chile, Bolivia, Mexico, Turkey and Indonesia.
Croda and its colleagues will continue to analyze the efficacy of different COVID-19 vaccines against P.1 and other variants with larger groups of people. In the next two weeks, they plan to look at data from Sao Pãulo, where more than 7 million people have been vaccinated with CoronaVac or the AstraZeneca vaccine. According to Jason Andrews at Stanford University, who works with the Brazilian research team and is co-author of the pre-print, it is a top priority. “It is critical to determine when vaccines are no longer effective against emerging variants,” he says. ‘What is a question of when rather than as. ”