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Sinovac’s COVID-19 vaccine produces antibody response in mid-stage study

Level of antibodies in vaccinated group lower than recovered COVID-19 patients

Chinese biotech Sinovac’s COVID-19 vaccine produced neutralising antibodies in a mid-stage trial, although the levels in the vaccinated group were lower than those observed in recovered COVID-19 patients.

The results from phase 1 and phase 2 trials, published in The Lancet Infectious Diseases, evaluated the CoronaVac vaccine in over 700 participants.

The primary immunogenic endpoint in the trials was the seroconversion of neutralising antibodies to the SARS-CoV-2 virus, which causes COVID-19. Seroconversion is defined as the time period during which antibodies develop and become detectable within the blood.

In the phase 2 trial, immune responses were ‘much better’ than those seen in the phase 1 trial, with seroconversion rates coming in at above 90% in both the 3μg and 6μg dose groups.

In addition, the researchers found that a more robust antibody response was generated and ‘longer persistence’ could be expected in the day 0 and 28 vaccination schedule compared to the day 0 and 14 schedule.

However, the study also found that the level of neutralising antibodies induced by the vaccine at day 28 was lower than that seen in patients who had recovered from COVID-19.

The researchers maintained that the vaccine could still provide ‘satisfying protection’ against COVID-19. This conclusion was based on researchers’ previous experience with other vaccines and preclinical data involving macaques.

'The antibody level itself might not be the key for a successful COVID-19 vaccine, but rather the establishment of a recallable specific immune response to SARS-CoV-2,' the researchers wrote.

'Furthermore, the efficacy of the investigational vaccine and its surrogate endpoint need to be determined in a future phase 3 trial,' they wrote.

Last week, a late-stage trial of Sinovac’s vaccine was halted in Brazil after a participant death was reported.

According to Reuters the death was reported as a suicide, with the Butantan Institute Biomedical Center, where the vaccine is being evaluated, adding that the event had ‘no relation’ to the vaccine.

Butantan Institute director Dimas Covas told a congressional hearing earlier this week that, if the vaccine is approved by Anvisa, Brazil’s health regulatory authority, the Institute is expecting to have 46 million doses of CoronaVac available in January.

Article by
Lucy Parsons

18th November 2020

From: Research



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