A new Hong Kong research showed those who have received the BioNTech COVID-19 vaccine have 10 times more antibodies compared to those who were given Sinovac, with the latter producing levels of the virus-targeting proteins that were either similar or lower compared to the naturally occurring ones seen in recovered patients.
The study results by the University of Hong Kong, AsiaOne reported, could suggest the need for "substitute strategies," including booster shots to enhance antibody concentrations and protection of Sinovac recipients against COVID-19; the researchers said.
The antibodies' presence is an indication of the previous infection, or that a COVID-19 vaccine is working to protect a person, although the proteins' quantity that the body generates to identify and neutralize the COVID-19 does not correlate directly to the immunity level.
Nevertheless, there is growing evidence that higher levels correspond generally with a stronger and longer-lasting shield against infection, experts explained.
The difference in Concentrations of Neutralizing Bodies
In their study, Benjamin Cowling and Gabriel Leung, leading epidemiologists, together with Malik Peiris, a virologist, wrote that the difference in concentrations of neutralizing bodies identified in their work could translate into significant differences in vaccine efficacy.
Cowling, the lead researcher, said in an interview that moderate levels of protection were still better compared to none at all and urged Hong Kong residents to get vaccinated.
Hong Kong had administered over 4.5 million doses of COVID-19 vaccines as of yesterday, some 2.6 million of German-manufactured BioNTech, and roughly 1.8 million mainland China-manufactured Sinovac.
Nevertheless, its vaccination initiative has lagged since its onset in late February, and only roughly a quarter of the population of the city is fully vaccinated.
BioNTech vs. Sinovac Recipients
For the antibody research, HKU researchers recruited more than 1,400 health care workers from public and private hospitals and clinics around the city. They collected samples of blood from them at different intervals.
In the first batch of over 90 fully vaccinated participants, antibody concentration for the 63 recipients BioNTech recipients rose significantly following the first dose and again after the next and second jab.
The 30 recipients of Sinovac, on the other hand, had low concentrations of antibodies after their first vaccine and moderate ones after the second injection.
Through the use of a gold standard approach also called PRNT, Cowling said, study authors found the average antibody levels of a subset of 12 recipients of BioNTech to be 10 times higher at 269, compared to those of an equal number of people in the Sinovac group, which clocked in at 27.
The study authors also found that the recipient of BioNTech with the lowest antibody level still had more than the Sinovac recipients with the highest.
Essentially, Sinovac-produced antibody levels were judged about similar to or a little slower than those detected in recovered COVID-19 patients.
BioNTech with 95-Percent Efficacy
According to Cowling, the gap between the two COVID-19 vaccines was consistent with the discrepancies the manufacturers reported in their third-phase clinical tests, which found BioNTech to 95 percent efficacy, as reported by the Centers for Disease Control and Prevention, compared to 50.7 percent for Sinovac.
He added, still, the most recent study provided an unusual head-to-head comparison of two COVID-19 vaccines. That made it priceless to scientists given the trials of the manufacturers' involved sample groups and sizes, making direct comparisons for their results challenging.
A similar South China Morning Post specified, finding suggested a potential need for Sinovac recipients, specifically the elderly, who had weaker immune responses to vaccines, to receive a third shot as a booster, said Cowling.
He also said the recipients of both vaccines had detectable antibodies a month after their second vaccines although he could not say for sure what it might mean for a government plan to cut short quarantine periods for some vaccinated travelers if they need to show proof of antibodies.
If it was unclear, he noted, whether some commercial laboratories would be sensitive enough to pick up low levels of antibodies.
Related information about COVID-19 vaccines is shown on the South China Post's YouTube video below: