The BioNTech and Sinovac vaccines are significantly less effective against Omicron subvariants BA.4 and BA.5 compared to the original virus strain, according to a new study.
The study, jointly conducted by the University of Hong Kong (HKU) and the Chinese University of Hong Kong, found that the levels of antibodies produced against BA.4 and BA.5 after receiving three doses of BioNTech or Sinovac vaccines were lower than those produced against the original virus strains by more than 10 times.
The research team analyzed the serum antibodies of 104 patients. Of the 104 samples, 60 had not been infected with COVID-19. Among them, 20 people had received three doses of BioNTech vaccine, 20 had received three doses of Sinovac vaccine, and 20 had received two doses of Sinovac vaccine and one booster dose of BioNTech vaccine.
Another 44 had been infected with COVID-19, 20 of whom had been infected with the original virus strain and the remaining 24 had been infected with BA.2, including 17 people who had received different doses of vaccine and seven who had not received any injection.
The team cited previous research showing that an antibody level of 25.6 is required to prevent symptomatic infection.
The results showed that after receiving three doses of the BioNTech vaccine, the subjects’ antibody levels against the original virus strain was 320, and the antibody levels against BA.4 and BA.5 decreased to 28.3 and 20.7, respectively. After receiving three doses of Sinovac vaccine, the antibody level against the original virus strain was only 65, and the antibody level against both BA.4 and BA.5 fell to 5.4.
The antibody levels against BA.4 and BA.5 were 6.8 and 5.9, respectively, in those who had been infected with the original strain. The antibody level against both BA.4 and BA.5 was 36.9 in people infected with BA.2 after injection, which was higher than that in other groups.
For BA.5, only 20 percent of those who received three injections of BioNTech vaccine met the standard of preventing infection, while none of those who received three injections of Sinovac vaccine met the standard for BA.2 or BA.5.
“Either BioNTech or Sinovac was found with antibody levels falling against the BA.4 and BA.5 virus variant of COVID,” said Leo Poon, a professor and head of the Division of Public Health Laboratory Science at HKU.
According to Poon, the data reflect BA.4 and BA.5 having stronger immune escape ability. People who have taken three shots of vaccine or have been infected with COVID-19 are both likely to be infected.
However, the mixed immunity brought by the vaccine and the infected virus produced higher levels of antibodies against BA.4 and BA.5 than other groups, which had a certain effect on preventing the infection of variant virus strains.
“Both types of vaccines can contribute to reducing the risk of death and appearing serious symptoms when people were infected with COVID if they were triple-vaccinated,” Poon said.
