CoronaVac vaccine against the “Amazon” strain of coronavirus: results from Brazil

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The effectiveness of the CoronaVac vaccine from Sinovaс Biotech in the country affected by the “Brazilian” strain of coronavirus after two doses reaches only 42% protection against COVID-19 with symptoms. We are talking about the effectiveness in the elderly from 70 years and older, write in the preprint of the study on medRxiv.


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For a study from January 17 to April 29, 2021 in the state of São Paulo (Brazil) during the wide spread of the P.1 strain, 7950 matching pairs were selected from 26 433 cases of COVID-19 and 17 622 people from the control group with a negative test result ” case-control “. The average age is 76 years.

Vaccine efficacy was 18.2% between days 0-13 after the first dose and 41,6% after 14 or more days after the second.

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Efficacy 14 days after the second dose decreased with increasing age and was 61,8% for age 70-74 years, 48,9% – 75-79 years old and 28% – among those who are 80 years old and more.

“No significant protection was observed until the completion of the two-dose regimen. The results highlight the need for continued non-pharmaceutical interventions (masks, distance, etc.) ed.) during the mass vaccination of CoronaVac “, the authors conclude.

The study does not indicate how the vaccine protects against severe covid disease, hospitalization, and death. However, as practice shows, all the SARS-CoV-2 vaccines approved by the WHO for emergency use with this at least do a good job, saving lives.

See also: AstraZeneca vaccine ineffective against mild-to-medium “South African” covid – numbers

Another study in Brazil tested the rate of seroconversion (the appearance of antibodies) to the S- and N-proteins of the coronavirus after CoronaVac. Twenty days after the second dose, 97% of health workers had seroconversion for S1 protein and 52% for N protein.

CoronaVac is a traditional vaccine; it contains inactivated (killed) whole viral particles of SARS-CoV-2, which makes it possible for the immune system to familiarize itself with its various antigens, and not only with the S-protein, as in mRNA and vector vaccines. Used in China, Chile, Bolivia, Mexico, Turkey, Indonesia, Brazil and Ukraine.

In April, Brazil reported that one dose of CoronaVac per ~50% effective against symptomatic COVID-19. Moreover, one dose is more effective in women than in men (data from Turkey).

Also in April, Chile announced that CoronaVac’s ~89% cases protects against hospitalization with COVID-19.

In mid-May, Indonesia wrote that the effectiveness of CoronaVac in real conditions is even higher than in clinical trials.

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