The government has announced that eligible persons under certain groups can receive a third dose of the COVID-19 vaccine starting from November 11.
The extra dosage was claimed to boost immunity in recipients, as the first two jabs’ protection will fade after a few months of taking the vaccine. The same situation is seen in both BioNTech (also known as Pfizer) and Sinvovac shots. However, the number of antibodies triggered by the Sinovac shot seems to decrease at a much higher rate.
According to a Chinese laboratory study, participants who received two doses of Sinovac jabs four weeks apart only have 35.2% neutralizing antibodies above the detectable threshold level, six months after the second shot. Hong Kong political figures, including Regina Ip Lau Suk-yee and others, have admitted that the level of neutralizing antibodies has dropped to zero about six months after Sinovac shots.
According to the government, individuals who are classified as priority groups for getting a third dose include:
- Certain groups of immunocompromised patients (e.g. cancer patients, organ transplant recipients, advanced-stage HIV patients, and patients taking active immunosuppressive drugs). Their third dose should be administered at least four weeks from the second dose.
- Those who have received two doses of the Sinovac vaccine and with a higher risk of infection (e.g. elderly aged 60 or above, healthcare workers, persons with chronic illnesses). Their third dose should be administered at least six months from the second dose.
For people from the above groups, they can choose to either get a Sinovac shot or a BioNTech one based on their personal choices.
However, which shot to take has raised some heated debate in Hong Kong. As the Sinovac vaccine is developed in mainland China, taking a shot has been seen by some as a sign of confidence in China and a patriotic act.
Chief Executive Carrie Lam has already chosen Sinovac for her first two shots. For her third, she has the option of choosing the German-made BioNTech or sticking to the Chinese-manufactured vaccine. Despite medical experts saying that taking BioNTech as a booster would allow a higher level of antibodies to remain after a prolonged period, Lam revealed that she would continue to put her faith in Sinovac.
When asked the reason, Lam said that there is a myth about a high count of antibodies. “According to my understanding, it’s not the higher the count of antibodies, the better, but whether there are enough,” she said.
However, experts seem to disagree with Lam’s view on antibodies. Pandemic adviser and microbiologist Ho Pak-leung said that it is difficult for others to understand Lam’s remarks as it is her personal opinion. Ho was unwilling to directly respond to her comments but emphasized that it is surely better to have a higher level of antibodies.
Another one of the government’s advisers, David Hui Shu-cheong also called Lam’s remarks a ‘personal opinion’. Hui pointed out that a high level of antibodies would minimize the symptoms when infected and hence provides better protection. He recommended people who had two jabs of Sinovac change to BioNTech for their third for a slower fall rate of neutralizing antibodies.
While Hong Kong’s focus is on which shot to take as a booster, the global third-jab debate remains on whether it is needed. Countries including the US, UK, Israel, Germany, and France, have decided to offer boosters to older adults and people with weak immune systems.
The World Health Organization (WHO) has repeatedly stated that data on the benefits of a booster shot is inconclusive. They believe that priority should be given to low-income countries with low vaccination rates. WHO Director-General Tedros Adhanom Ghebreyesus called the situation a “moral issue” when richer countries could afford to have a booster at the expense of developing countries that are not even vaccinating the first and second round.
On the other hand, vaccine experts in Hong Kong are considering the possibility of a fourth jab for some residents. Professor Hui has suggested a fourth dose six months after the third jab to ensure protection for groups with a weaker immunity system.