askST: Should you wait for new Covid-19 vaccines before taking your booster?

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SINGAPORE - Singapore is in the midst of a Covid-19 wave, with the Omicron sub-variants BA.4 and BA.5 accounting for about half of the total number of cases here as at last Tuesday.

With vaccine manufacturers such as Pfizer-BioNTech and Moderna developing updated vaccines that target these variants, The Straits Times answers some questions on what it all means.

Q: If I have not taken my booster, should I wait for the new Covid-19 vaccines before doing so?

A: The Ministry of Health (MOH) and the Expert Committee on Covid-19 Vaccination strongly recommend that those who are eligible for boosters take their jabs without delay.

This is so that they can stay protected against Covid-19, particularly in the light of the recent increase in cases, an MOH spokesman told ST.

A study by Moderna showed that its updated vaccine shot increased virus-neutralising antibodies by more than fivefold against the Omicron sub-variants in approximately 800 participants regardless of prior infection, one month after it was given.

While the results show that the updated vaccine protects well against the latest sub-variants, Health Minister Ong Ye Kung said the current vaccine formulation works very well in preventing those who have taken it from falling very sick.

He urged those who have not taken their boosters despite being eligible to do so instead of waiting for the updated vaccines.

Q: What are these new vaccines?

A: A Reuters article last month said Moderna, Pfizer and Novavax had been testing updated vaccines based on the first BA.1 Omicron variant that became dominant last winter, driving a massive surge in infections.

This was followed by Moderna saying its updated vaccine worked well against the BA.4 and BA.5 sub-variants.

The report added that the World Health Organisation plans to assess the effectiveness of vaccines made for Omicron.

Singapore is reviewing the safety and effectiveness of these vaccines and may be able to roll them out by the year end if they are approved.

Unlike influenza vaccines that manufacturers are allowed to make annual adjustments to, so as to align with circulating strains, the Reuters article said regulators have asked companies to run clinical trials to prove their new Covid-19 vaccines work better.

For their part, vaccine makers are pushing for a flu-like model that would allow them to retool their shots to combat new variants more easily.

Q: How infectious are the new sub-variants?

A: The sub-variants BA.4 and BA.5 were first detected in Singapore in mid-May and are now poised to account for 70 per cent to 80 per cent of cases here.

While the variants are said to have a significant growth advantage over the BA.2 variant, Mr Ong does not expect the current Covid-19 wave to be as severe as the Omicron wave earlier this year.

"This is because many more of us have gained stronger immunity, either through booster shots or recovery from infections, and this will significantly impede the circulation and transmission of the BA.4 and BA.5 viruses," he said.

According to The New York Times, the new sub-variants do not have markedly divergent symptoms from earlier versions of Omicron.

People infected with them may develop a cough, runny nose, sore throat, fatigue, headaches and muscle pains, but are less likely to lose their senses of taste and smell, or to experience shortness of breath, as compared with those infected with Delta or other variants of the coronavirus.

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