While the booster vaccine is still a debatable issue among healthcare experts, many Singaporeans after getting both the doses of a vaccine, decided to get the third jab, fearing they would catch Covid-19 due to dramatically low antibody count.

One of those concerned Singaporeans was Soh, aged 43, who took an antibody test to know about her immunity levels after receiving both the doses of a Chinese vaccine developed by Sinovac. When the test results came, she found that the antibody count was 140—which, according to her doctor, was about 10 times lower than what someone would have after two Pfizer-BioNTech doses, which, along with Moderna shots, are given to all residents of the island nation over the age of 12.

As per a report by the South China Morning Post, Soh said: “My doctor had repeatedly advised me to go for Pfizer or Moderna, but I decided to give Sinovac a try as I wanted to see how strong the vaccine is.”

She, who works in the banking industry, took this decision to go for Sinovac jab after reading reports about the low efficacy of the vaccine compared to other jabs and wanted to know for sure whether all those reports are true, but the antibody test result “disappointed” her. Soh paid around $15 (Rs 1096) for two doses of the Sinovac vaccine at a private clinic. Her husband and sister also took Sinovac vaccines and their antibody counts were found to be at 400 and 9, respectively.

Following a high increase in domestic cases in Singapore last month and concerns about contracting the novel virus, all three of them chose to get the third jab. But this time from Pfizer-BioNTech. When Soh took another antibody test after the third shot, the numbers jumped to 1,900.

Dr Leong Hoe Nam, an infectious diseases specialist at Singapore’s Rophi Clinic, one of 31 private clinics authorised to dispense Sinovac vaccines, said an increasing number of patients had discovered that the Chinese-made vaccine provided insufficient protection. He told SCMP: “They took the Sinovac shots, did the blood test and saw low antibody levels, then opted for Pfizer as the third dose.”

Although antibody counts do not always correlate with an individual's immunity, researchers believe they do provide some indication of protection. Antibody levels of 1,300 to 2,000 international units per millilitre are common for someone who has taken two Pfizer dosages, according to Leong, “but for Sinovac, it is zero to 40. We have a few with 200 to 300”.

Vaccination experts throughout the world are debating the merits of a third dosage or booster shot. Countries like Israel are issuing them in response to an uptick in cases, taking no chance with the Delta variant’s spread. But some experts, including the World Health Organization (WHO) have highlighted ethical concerns, pointing out that vaccination shortages in many parts of the world have left people vulnerable to the spread of more lethal strains.

However, in the case of Singapore, officials said that they were considering giving booster doses to seriously immuno-compromised people, such as cancer patients.

Since the initial batch of 200,000 Sinovac vaccine doses arrived in February, more than 85,000 people in Singapore have got two doses. They are among the 80 per cent of Singapore's 5.7 million residents who have received full Covid-19 vaccinations as the country prepares to reopen its borders.

With over 9 per cent of Singapore's population under the age of 12 not currently eligible for vaccination and some having received only one jab, around 460,000 people have yet to receive a single dose. The government has built up roughly 30 walk-in vaccination centres and deployed mobile vaccination units for older populations to maintain high immunisation rates.

It has also made allowances for what appears to be a continuing demand for Chinese vaccines. The health ministry reported on 10 August that new Sinovac shots will be arriving in four to six weeks after the initial shipment from February was practically depleted. Due to the scarcity of supplies, some people have already turned to the illegal market.

People had auctioned their Sinovac appointments on the mobile marketplace Carousell, offering them for 50 Singapore dollars to 80 Singapore dollars. However, such posts were later removed by the authorities.

Recently, some private hospitals and clinics began inoculating people with another Chinese vaccine, developed by Sinopharm. It is worth 90 Singapore dollars (Rs 4,893) and 100 Singapore dollars (Rs 5,436) for two doses. More than 6,000 local people have expressed interest in receiving the Sinopharm vaccine, according to IHH Healthcare Singapore, while Raffles Medical Group has received more than 10,000 registrations thus far, said reports.

Dr Jeremy Lim, an associate professor at the National University of Singapore's Saw Swee Hock School of Public Health, said immunisations were very essential in reducing severe Covid-19 cases. He told SCMP: “Hence, it’s really about which vaccine best fits one’s world views and concerns, no matter how justified or otherwise. The clamour for the Chinese vaccines is thus understandable given the imperative for vaccination.”

However, Dr Leong from the Rophi Clinic said that the results of antibody tests mostly confirmed that the Sinovac vaccine is not particularly effective. But an infectious diseases specialist Dr Ling Li Min pointed out that antibody tests measured “just a single snapshot of a subset” of a complicated human immune system.

Even though at this moment there is no established cut-off figure to determine a sufficient immunological response after the Covid-19 vaccination, according to experts, the logical idea is that a higher antibody count is undoubtedly better.

Third covid vaccine

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