The CoronaVac vaccine, by Chinese company Sinovac Biotech has proven to be 66% effective against symptomatic COVID-19. But this improves to 88% against hospitalization, 90% against ICU admissions, and 86% against deaths. However, antibody levels have declined below acceptable levels after 6 months in most cases. But the good news is a booster jab reinstates immunity for the Sinovac product.
Chinese Researchers Report Finding in MedRxiv
MedRxiv is an internet site hosting unpublished e-prints of health science manuscripts. This helps ensure breaking medical news is available early. However this comes at a cost of lacking peer review and confirmation. But in this instance, the research is by leading experts in the field and we regard it as credible.
Evidence a Booster Reinstates Immunity for Sinovac
Reuters published an update on July 27, 2021, summarizing the research report. But we’ve included a link to the MedRxiv research at the end of this post, if you would like to know more.
1… The findings come from analysis of blood samples from healthy adults aged 18 to 59.
2… Some 540 vaccinated subjects received a third, booster shot at different intervals.
3… These intervals were 42 days, 56 days, 194 days or 208 days according to South China Morning Post.
3… Antibody levels rose ‘slightly to moderately’ after the two shorter intervals, but the benefits was lost after six months.
4… However, the two longer intervals led to a ‘strong boost in immune response‘.
5… There was a ‘three-five fold increase in neutralizing antibody titer concentrations 28 days after the second dose’.
If a booster reinstates immunity for the Sinovac product, would other vaccines perform similarly? The Chinese researchers believe the driver may have been an anamnestic response to an antigen foreign substance immune systems previously encountered.
They recommend booster doses should be timed according to vaccine immunogenicity effectiveness, the local epidemic situation, the infection risk, and the vaccine supply. However, Sinovac is an inactivated virus vaccine. Do you suppose other vaccines might behave differently?
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