Antibodies caused by Sinovac Biotech’s COVID-19 vaccine dropped below a significant threshold for most recipients from about six months after a second dose, but a third injection had a strong potentiating effect, a lab study found.
Chinese researchers reported the findings of a study of blood samples from healthy adults between the ages of 18 and 59 in an article published Sunday that has not been peer-reviewed.
Of the participants who received two doses, two or four weeks apart, only 16.9% and 35.2%, respectively, had neutralizing antibodies above an investigator-defined threshold below which the antibody level is considered low or undetectable. six months after the second injection, the paper said.
Those measurements were based on data from two cohorts with more than 50 participants each, while the study gave third doses of the vaccine or placebo to a total of 540 participants.
Researchers said it was unclear how the decrease in antibodies would affect the effectiveness of the injection, as scientists have yet to determine the threshold of antibody levels for a vaccine to prevent the disease.
Aside from durable antibodies, other components in the human immune system, such as T cells and B-cell memory generated by the vaccine, may also contribute to protection, according to researchers involved in the study, although the study did not provide data on that produced factors.
“In the short to medium term, it should ensure that more people complete the current schedule of two doses of CoronaVac (Sinovac’s vaccine),” the paper said.
Participants in some cohorts who received a third dose of Sinovac injection about six months after the second showed approximately a 3-5-fold increase in antibody levels after an additional 28 days, compared to levels taken four weeks after the second injection. perceived.
Since the end of June, Sinovac has delivered more than 1 billion doses of the vaccine, a major vaccine tool in China, Brazil, Indonesia and Chile.
Other COVID-19 vaccine manufacturers are trying to get approval for booster shots. Pfizer and partner BioNTech said earlier this month they planned to ask US and European regulators to approve a booster dose of their COVID-19 vaccine within weeks, based on evidence of a greater risk of infection. six months after inoculation and the spread of the highly contagious Delta variant.
Siti Nadia Tarmizi, a senior official at Indonesia’s health ministry, told Reuters on Tuesday that clinical data from the country showed that the reduced antibody level is still sufficient to provide protection, without providing details.
She said the immunization advisory board recommends booster vaccination 12 months after the second dose.
Indonesia this month started giving booster shots produced by Moderna to medical personnel, including those who had received Sinovac doses.
Philippine Health Minister Francisco Duque said on Tuesday there is no recommendation from the country’s panel of vaccine experts on giving a booster shot, but experts are discussing the possibility.
Turkey has already started offering a third dose of Sinovac or Pfizer to some people who have received Sinovac injections.
The research paper on Sinovac’s vaccine said the study did not test the effect of the antibodies against more transmissible variants, and further research was needed to assess the duration of the antibodies after a third injection.
The study was conducted by researchers from the disease control authorities in Jiangsu Province, Sinovac and other Chinese institutions.
(Except for the headline, this story has not been edited by NewsMadura staff and has been published from a syndicated feed.)