A study by Chinese researchers has indicated the antibodies triggered by Sinovac Biotech’s CoronaVac COVID-19 vaccine dropped below the required threshold about six months after the second dose injection in most recipients.
Therefore, a third dose or booster injection is needed to increase the antibody count.
In the study released on Sunday 25th July 2021, Chinese researchers revealed that only 16.9 percent of participants had antibodies above the necessary threshold after six months of being injected with two doses of Sinovac vaccine two weeks apart. Meanwhile, only 35.2 percent of participants had antibodies above the main threshold after being injected with the Sinovac vaccine four weeks apart.
The researchers said it was unclear how the drop in antibodies would affect the vaccine’s effectiveness. Scientists do not yet know exactly what threshold levels of antibodies for a vaccine that can prevent COVID-19 infection are.
They also found that participants in some groups who received the booster of Sinovac vaccine after six months of injection of the second dose showed an increase of approximately three to five times in antibody levels after 28 days of the third injection, compared to antibodies seen in recipients of the Sinovac vaccine of two doses with an injection delay of 28 days.
These findings are based on a study of blood samples of healthy adults aged 18-59 years, consisting of more than 50 participants in each group and 540 participants were to be injected with a third dose of vaccine or a placebo.
The option of injecting the third dose of vaccine is being discussed by several experts to increase the effectiveness of the vaccine against the new COVID-19 variant and decrease the efficacy of the vaccine.
Spokesman for the COVID-19 Task Force Wiku Adisasmito responded that, if it is found that the antibody condition is no longer sufficient to provide individual protection, the next stage of vaccination is required.
However, said Wiku, each vaccine has the ability to cause different antibodies in each person and population. The condition of antibodies can be known if the individual undergoes an examination.
Wiku also said that antibody surveys conducted on a population must use a representative number of samples. After that, the data can be analysed and conclusions were drawn.
“The Indonesian government has not conducted a comprehensive survey to see antibody protection in the community. But the government is stepping up and expanding vaccination coverage,” said Wiku.
Furthermore, spokesperson for COVID-19 vaccination from the Health Ministry, Siti Nadia, said Indonesia’s clinical data showed a decrease in antibody levels but it was still sufficient to provide protection, without providing details.
“The results of this research at Padjadjaran University are still effective against the COVID-19 virus,” said Nadia.
The immunisation advisory board has recommended a booster injection 12 months after the second dose. Indonesia itself has started booster injections to health workers using the Moderna vaccine.
So far, there has been no discussion on the third dose of vaccination for the general public because the World Health Organisation (WHO) has not published recommendations for the third stage of vaccination.
The WHO earlier this month said that boosters would either be needed or not to maintain protection until further data is collected. Despite that, several countries are planning for a booster campaign and Pfizer and its partner BioNTech are preparing to ask the U.S. and European regulators to approve a booster dose.