People gain a higher level of Covid-19 antibodies from getting one jab after infection compared to three jabs of the same vaccine, a team led by respiratory expert David Hui Shu-cheong found.
The team conducted a study from February 2020 to November last year to understand the effect of Omicron variant BA.2 on people receiving different Covid vaccines.
The results showed that people who received three doses of the BioNTech vaccine had higher levels of neutralizing antibodies than those who received three doses of Sinovac. In addition, those who received one dose of vaccine after infection had higher levels of antibodies than those who received three doses of the same vaccine.
The study recruited 120 participants and divided them into six groups. Non-infected groups included people who received three doses of Sinovac, three doses of BioNTech, two doses of Sinovac, and one dose of BioNTech. Infected groups were unjabbed, those who received one dose of Sinovac after recovery and one dose of BioNTech after recovery.
Three to five weeks after the last jab, the participants were asked to undergo neutralization tests, which could determine the effect of the Omicron BA.2 variant virus on their level of neutralizing antibodies.
The results showed that those who had received one dose of BioNTech vaccine after being infected had the highest geometric mean titer (GMT) of serum neutralizing antibodies at 144.2, followed by those who received three doses of BioNTech at 95.1. The GMT level for those who had received one dose of Sinovac after infection was 28.3, while those who received three doses of Sinovac saw 9.5. In addition, the GMT level for recovered patients who had never been jabbed was 9.
The study also showed that unvaccinated individuals were more likely to be infected with Omicron BA.1 after being infected with Omicron BA.2 due to insufficient cross-neutralizing antibodies.