A new study from the University of Hong Kong has found that two doses of Sinovac, China’s Covid-19 vaccine administered in many countries provide “insufficient” antibodies against the Omicron variant of the virus driving the current pandemic.
The variant, first isolated in South Africa in late November, has been found to multiply about 70 times faster than the original and Delta versions of the virus, in samples of bronchial tissue taken from the tubes that link the lungs and windpipe.
It’s predicted to become the dominant variant in many parts of the world by the beginning of 2022.
However, the study also found that the Omicron variant grew some 10 times more slowly in lung tissue. The study’s authors say that this could explain why the variant seems to cause less severe symptoms, said a report in The Guardian newspaper.
The University of Hong Kong study’s results are sounding alarm bells as different countries report their first Omicron cases this week. Those countries include China, where a traveller who returned to Tianjin tested positive for Omicron on Dec 9.
More than 2.5 billion doses of Sinovac and Sinopharm, another Chinese vaccine, have been administered in China.
The Financial Times quotes Nicholas Thomas, an associate professor at the City University of Hong Kong specialising in Chinese foreign policy and health security in Asia, as saying that Omicron “has left the Chinese vaccines even more ineffective against the threat posed by Covid.”
“The challenge for the Chinese authorities will be [to] re-engage their population’s commitment to another round of vaccines.”
The University of Hong Kong tested 25 people who had received two doses of Sinovac, and another 25 who had taken two doses of the Pfizer-BioNTech vaccine to check their antibody levels.
None of the 25 who took Sinovac showed enough antibodies in their blood serum to neutralise the Omicron variant, five of those who took the Pfizer shots had detectable neutralising antibodies against the new variant.
The researchers are saying that the Pfizer-BioNTech vaccine has between 20 and 24 per cent “efficiency” against Omicron.
Meanwhile, Pfizer announced on Dec 8 that three doses of its vaccine are able to neutralise the variant.
Sinovac is not the only vaccine that appears unable to produce neutralising antibodies against Omicron.
Studies from Oxford University and the Medical University of Innsbruck indicate that those who had taken double jabs from the Oxford/AstraZeneca vaccine also showed no measurable antibodies that would protect them from the new variant.
A certain level of antibodies must be present in the body in order to prevent symptomatic Covid infections.
But even as studies have shown that the Omicron variant weakens antibody protection provided by vaccines, people who have received two vaccine doses will still have some protection from the severe disease because this is mediated by T cells and B cells instead of antibodies.
Singapore’s Ministry of Health offered another finding on Wednesday from a study by the National Centre for Infectious Diseases (NCID) and the Ministry of Health’s (MOH) COVID-19 Data Management and Analytics Team.
People who have taken two Sinovac jabs “were observed to have lower protection against severe disease from infection with the Delta variant compared to those who received two doses of Pfizer-BioNTech/Comirnaty or Moderna mRNA vaccine”, MOH said.
This data, MOH added, “supports the need for three doses of Sinovac-Coronavac vaccine as a primary series.”
Local data has shown that two doses of the Sinovac-CoronaVac vaccine were 60 per cent effective against severe disease. This is lower than the 90 per cent for Pfizer-BioNTech/Comirnaty vaccine, and 97 per cent for the Moderna mRNA vaccine. /TISG
Read also: MOH: People with 2 Sinovac, Sinopharm jabs, need 3rd to be considered ‘fully vaccinated’
MOH: People with 2 Sinovac, Sinopharm jabs, need 3rd to be considered ‘fully vaccinated’