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Can people receive three jabs of Sinovac's CoronaVac vaccine?

This article was published on
May 18, 2021

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We do not yet know if Sinovac's COVID-19 third dose is safe or effective. A third injection is being tested in a Chinese clinical trial now. It is not recommended to have a third vaccine dose until more data has been studied and it has been deemed safe by health organizations.

We do not yet know if Sinovac's COVID-19 third dose is safe or effective. A third injection is being tested in a Chinese clinical trial now. It is not recommended to have a third vaccine dose until more data has been studied and it has been deemed safe by health organizations.

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What our experts say

Sinovac's COVID-19 vaccine, called CoronaVac, is currently being tested in a Chinese clinical trial to determine whether or not a third shot will help improve immunity against the virus. Participants of the trial get a third shot eight months after their second jab. As of now, we don't know if receiving a third shot is safe. We also don't know if it will improve protection against the virus. Because of this, it is not recommended that people receive a third CoronaVac dose.

Previous clinical trial data from China's CoronaVac showed that the vaccine's efficacy ranged from roughly 50% to 84% against symptomatic COVID-19 infections in several countries. The largest study involved 10.5 million people. It evaluated vaccine recipients in Chile at least 14 days after they received their second dose. The study showed that CoronaVac was 67% effective at preventing symptomatic COVID-19. It was 85% effective at preventing hospitalizations and 80% effective at preventing deaths caused by COVID-19.

Interestingly, Brazilian researchers found that the vaccine has a higher efficacy (62.3%) when the second dose is given 21 or more days after the first injection, rather than 14 days between shots (50.7% efficacy).

Context and background

Several countries have put in orders for third shots of some vaccines in case the boosters are shown to be beneficial and efficacious in helping increase protection against the virus. Three jabs of Sinovac's CoronaVac vaccine is not recommended by the World Health Organization or national ministries of health, though it is being studied in some countries now.

Resources

  1. Covid-19: Chinese vaccines may need changes to improve efficacy, admits official (The BMJ)
  2. Safety, tolerability, and immunogenicity of an inactivated SARS-CoV-2 vaccine in healthy adults aged 18–59 years: a randomised, double-blind, placebo-controlled, phase 1/2 clinical trial (The Lancet)
  3. PDF [599 KB] Figures Save Share Reprints Request Safety, tolerability, and immunogenicity of an inactivated SARS-CoV-2 vaccine (CoronaVac) in healthy adults aged 60 years and older: a randomised, double-blind, placebo-controlled, phase 1/2 clinical trial (The Lancet)
  4. Evidence Assessment: Sinovac/CoronaVac COVID-19 vaccine (World Health Organization)
  5. Clinical study proving greater effectiveness of Coronavac is sent to Lancet (CNN Brasil)
  6. First Dose of Chinese Covid-19 Vaccine Offers Little Protection, Chile Learns (The Wall Street Journal)
  7. Sinovac COVID-19 vaccine appears safe, triggers antibodies in trial in children: researcher (Reuters)
  8. Low Efficacy of Chinese Shots Sows Concern on Global Rollout (Bloomberg)
  9. China Sinovac Shot Seen Highly Effective in Real World Study (Bloomberg)
  10. Sinovac: Brazil results show Chinese vaccine 50.4% effective (BBC News)
  11. Can you mix COVID-19 vaccine doses to boost immunity? China wants to find out (Fortune)
  12. Coronavirus vaccine: Hong Kong resident got three Covid-19 jabs after not telling doctor or staff about medical history (South China Morning Post)
  13. Sinovac shot cuts risk of symptomatic Covid-19 in half, study says (South China Morning Post)

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