To boost or not to boost: The pros and cons of getting a third COVID shot

With the government offering a free booster dose from September 24 and the paid option of the Moderna vaccine available soon, millions of Thais are thinking hard about whether or not to get a third shot.

Dr. Apisamai Srirangson, spokesperson of the Centre for COVID-19 Situation Administration (CCSA), says 3 million Thais who were double-jabbed with Sinovac’s inactivated COVID-19 vaccine between March and May will soon get an SMS about their appointment for a third jab.

“We will be giving AstraZeneca [viral-vector vaccine] as the booster,” she announced last week.

Millions of Thais have also prepaid for the Moderna vaccine, which is made with innovative mRNA technology. But most of them will have already received other COVID-19 jabs when the first batch of Moderna vaccine reaches Thailand next month. As a result, these people will now be pondering what to do with their already-paid-for doses.

Welcome or worry?

While frontline medical workers are eagerly welcoming booster shots that offer higher immunity in the face of significant infection risks, people, in general, are not that keen. COVID-19 vaccines, after all, are not without side effects and full protection is not guaranteed.

On September 18, a rescue worker described as healthy by his parents was found dead at home in Ratchaburi province after getting his third jab a day earlier. Doctors said the 40-year-old man died from blood-circulation failure.

One day later, Ratchaburi city mayor Sakchai Pisanphon revealed he had tested positive for COVID-19 despite having had two shots of Sinovac and a booster dose of AstraZeneca. He got his third jab on August 28.

Meanwhile, the World Health Organization says that it does not yet have sufficient scientific data to approve the widespread use of boosters. In the United States, health authorities only recommend a Pfizer booster for people aged 65 and up.

A million doses of vaccines to be administered on Mahidol Day (Sep 24th)

Thailand’s Ministry of Public Health plans to administer at least one million doses of vaccines on Mahidol Day (September 24th) to commemorate the late HRH Prince Mahidol of Songkhla, father of the late King Bhumibol Adulyadej, for his contribution to medical education in Thailand.

Thai research

To date, the Thai government has offered free shots of Sinovac, AstraZeneca, and Pfizer (the latter is also an mRNA vaccine). There is also an alternative option of Sinopharm jabs for those willing to pay. Like Sinovac, Sinopharm is an inactivated vaccine.

Research by the Mahidol University’s Faculty of Medicine Siriraj Hospital shows that immunity in people injected with two doses of Sinovac and then an AstraZeneca booster soars from 52 units to 1,558 units. Yet that level is still lower than from two shots of Pfizer, which lifts immunity to around 1,900 units.

Dr. Yong Poovorawan, who heads Chulalongkorn University’s Center of Excellence in Clinical Virology, has suggested a third shot will likely be necessary because it significantly raises immunity.

“After two doses of inactivated vaccine, the third shot could be a viral-vector type or an mRNA type [ie, Pfizer or Moderna],” he said.

The government is so far offering medical workers a choice of AstraZeneca or Pfizer for their third jab.

Should you get Moderna as third jab?

Dr. Sopon Iamsirithaworn, deputy chief of the Disease Control Department, said people can get two shots of Moderna if they have not received any COVID-19 vaccine before. However, those who have already been jabbed should consult a doctor before getting a Moderna shot, he said.

And people should not take a Moderna booster soon after receiving their second dose of AstraZeneca.

“Do not over-vaccinate yourself,” he warned.

Bangkok’s Praram 9 Hospital concurs. It advises against a Moderna booster for those who have had two shots of AstraZeneca, saying vaccinees in this case should wait for the next-generation COVID-19 vaccine.

However, the hospital said that people fully vaccinated with Sinopharm or Sinovac can receive Moderna vaccine about three to six months after their second shot.

Bangkok Hospital, meanwhile, suggests that those double-jabbed with AstraZeneca can get a shot of Moderna six months after their second shot.

Thonburi Healthcare Group advises that any vaccinee can get the Moderna booster if they wait at least three months after their second jab.

By Thai PBS World’s General Desk


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