Herd immunity first, booster shots later


THE debate over booster shots of the Covid-19 vaccine is heating up globally on concerns that the contagious Delta variant is capable of infecting fully vaccinated people.

The World Health Organisation (WHO) argues that it may be too early to push for Covid-19 booster shots, especially when many people around the world have not even received their first dose.

On Aug 26, Health director-general Tan Sri Dr Noor Hisham Abdullah said that the booster shots for those who have completed their Covid-19 vaccination will not curb the highly contagious Delta variant.

He said the current Covid-19 vaccines used in Malaysia have proven effective against the Delta variant, which resulted in the reduction of hospital admissions, intensive care unit (ICU) bed usage, and ventilators for its patients.

Currently, there are five vaccines approved under the National Covid-19 Immunisation Programme (PICK), namely Pfizer-BioNTech, Sinovac, AstraZeneca, CanSino Biologic, and the Janssen vaccine of Johnson & Johnson.

Focus on those unvaccinated

The Malaysian Public Health Physicians’ Association (PPPKAM) president, Datuk Dr Zainal Ariffin Omar said PICK should prioritise getting as many people as possible to be vaccinated before considering booster shots.

He said giving a booster shot to increase the efficacy for someone who already has protection should not be prioritised over those who have zero protection.

“There is no need to rush into giving booster shots to ward off the more transmissible Delta strain amid concerns over the mutation which has been categorised as a variant of concern (VoC).

“The mass vaccination must be prioritised before consideration can be given for a booster shot and that no one will be safe until everyone is,” he told Bernama recently.

As of Aug 28, some 61.1 percent of the country’s population or 14,297,962 individuals have completed both doses of the COVID-19 vaccine, according to the Covid-19 Vaccine Supply Access Guarantee Special Committee (JKJAV).

Dr Zainal said some countries provide the third dose for their citizens because they have sufficient supply and have achieved herd immunity.

But in Malaysia, he said there are still many people who have yet to be vaccinated.

“Some states, like Kedah and Kelantan have not reached even 40 percent of the fully vaccinated individuals… some also have been facing shortages of the vaccine.

“We have to focus on getting them vaccinated at least two shots to prevent the spreading of VoC. Yes, we have new variants now and might have other variants coming soon.

“But to achieve herd immunity we must get as many people to be vaccinated. Later on, when there is enough data and vaccines, then only we could consider to give them booster shots,” he said.

Still under study

With the spread of VoC, many countries consider giving booster shots or a third dose to prevent the mutation of the virus in the future, even for those who have completed the two-dose regimen.

Oxford-Astrazeneca vaccine co-developer, Prof Dr Teresa Lambe said this is not yet necessary, as it is more important to prioritise the first doses for as many people as possible globally.

“That’s actually one of the areas that I am working on in the lab and what we have done is to give a third dose of the Oxford-AstraZeneca vaccine to a small number of people, in the hundreds.

“What we are looking to see is whether the immune response is boosted and we have seen that with the third shot.

“But my interest will be to get first doses across the world to individuals who haven’t had any vaccine yet before we consider boosters.

“There is an onus on us to make sure the world is protected before we start looking to deliver boosters,” she said in a keynote address at the Third International Conference of Pharmacy and Health Sciences 2021 held virtually.

Proper plan on booster, mix-matching vaccines

On getting the different brands of the second dose in Covid-19 vaccines, Lambe said it does produce potent immune responses in mixing and matching regimes.

“I think when it comes to mixing regimes, priority should be given to those who have already received their first dose. Then, the second dose later (if they wish to get mixed vaccines, according to the time frame given),” she said.

(The timeframe for Pfizer is three weeks after the first dose, while AstraZeneca is between 9-12 weeks after the first dose).

“I have been involved in some studies looking at administering the Pfizer-BioNTech jab first or the ChaAdOx1 nCoV-19 (Oxford-AstraZeneca) first, then doing the other second (dose),” said Lambe.

“One regime is slightly more reactogenic but the immune responses in the mixed regimes do look good,” she said.

Dr Zainal said there is a need to have proper planning from the government whether to give mix-matching vaccines and booster shots to prevent the VoC of the virus.

“Right now, achieving herd immunity of two-dose vaccines should make it a priority. It might be confusing people if we implement either mix-matching vaccines or booster shots for now.

“If the government decides to kick-start such programmes, they should make preparation and proper planning to purchase enough vaccines for the boosters or mix-matching regime, as well as to avoid supply shortages,” he said.

Lambe advises the public to trust the regulator and take whatever brand of approved Covid-19 vaccine is offered to them without judging.

“For me, you need to look at the real-world effectiveness data, trust the regulator and trust the safety monitoring board et cetera to make the recommendations of the best vaccine for the people in your country.

“Take the vaccine you were offered, get the vaccine in your arm, make yourself safe and make the world safe,” she said. – Bernama

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