SINGAPORE – The Republic will be bringing in the latest Covid-19 vaccines by the end of October. The Health Sciences Authority has approved Pfizer’s new vaccine and is reviewing Moderna’s vaccine. Both are monovalent, targeting the XBB.1.5 Covid-19 strain. Is there really still a need for such vaccines now that the pandemic is over? For those who are due for their booster jabs, should they wait for the new vaccines? Here’s what the experts say.

Q: The pandemic is over, so why is Singapore bringing in more Covid-19 vaccines?

A: The pandemic may be over, but the virus is still circulating. In the week of Sept 3, more than 7,000 people here were diagnosed with Covid-19. While this is far lower than the numbers seen in April and May, which peaked at over 28,000 a week, it remains significant as 151 people were hospitalised that week, with two needing intensive care.

Health Minister Ong Ye Kung recently cautioned that with falling vaccination take-up rates here, “over time, our protection against Covid-19 will weaken”.

Urging people to get their booster shots, he said: “The virus has not gotten milder. It is we who have gotten stronger, through vaccinations and safe recovery from infections.”

In the first seven months of this year, 172 people died from Covid-19 in Singapore.

Q: But the new vaccines do not target the dominant circulating strains, so what’s the point?

A: It’s true that the new monovalent vaccines target a strain – the XBB.1.5 strain – that is no longer dominant, but experts say they do provide better protection than current bivalent vaccines against the various Covid-19 Omicron strains that are currently circulating.

Professor Hsu Li Yang, vice-dean of global health at the National University of Singapore’s Saw Swee Hock School of Public Health, said that while the new vaccines target the XBB.1.5 strain, they “will still generate a strong immune response that will protect against the current variants EG.5 (Eris) and BA.2.86 (Pirola)”.

Dr Asok Kurup, an infectious diseases specialist in private practice, said immunity from previous vaccines would have waned, so having vaccine updates is likely going to be a regular affair.

Associate Professor Lim Poh Lian of the National Centre for Infectious Diseases said: “There is good cross-protection between the different Omicron sub-variants. So it doesn’t matter that much that the sub-variant targeted is no longer dominant because the protection provided is fairly broad.”

Dr Sebastian Maurer-Stroh, executive director at the Agency for Science, Technology and Research’s Bioinformatics Institute, which tracks Covid-19 strains here, said the main circulating strains in Singapore today are the EG.5.1.1, HK.3 and EG.2, all of which are part of the XBB.1.5 family.

Q: The new vaccines are monovalent, which means they target just one strain. The vaccines currently used here are bivalent, targeting two strains. So aren’t the older vaccines better?

A: Not so, say the experts.

Prof Lim said the new vaccines are “fully targeted against the Omicron variant, which has been circulating for over a year now”. They therefore provide better protection against the Omicron variant “because the full amount of the booster – instead of just half of it – is targeted at Omicron”, she said.

Prof Hsu explained that including a non-Omicron strain may generate an immune response in our body to older variants “that might impair protection against newer variants of the virus”. 

Q: Since the new vaccines are better, there’s no point in getting a booster jab now, right? We should all wait for the new ones to become available here.

A: Both Prof Hsu and Dr Kurup say it would make sense to wait for the new vaccines, which should be available here by the end of October.

Prof Lim, however, urged people who answer “yes” to any of the following not to wait, but to get a booster now:

• Are you at risk of Covid-19 complications because of your age (the Ministry of Health recommends booster vaccines for people aged 60 and older) and medical conditions?
• Was your most recent booster vaccine more than 12 months ago?
• Do you plan to travel and what is the Covid-19 situation like at the travel destination?

She said: “Antibody levels generally drop over time, although immune memory persists. So it is important for medically vulnerable persons to be protected by strengthening their immunity with a Covid-19 booster, ideally within 12 months from their last dose.”

This is because “with open borders, more travel, and removal of restrictions such as face masks, new variants can arise and spread quickly”.

Q: Younger people are less likely to get seriously ill if infected, so do they really need to get a booster?

A: That is a personal decision.

Prof Hsu said that there is no real risk other than sore arms and a bit of fatigue if they had received the earlier doses uneventfully.

But he said: “The benefit is also negligible unless they have very strong reasons for wanting to minimise the risk of symptomatic Covid-19 for a couple of months.”

This is because the level of antibodies rises significantly two weeks after a booster, and remains high for several months, thus providing short-term protection against infection.

Young and healthy people who have had the “minimum protection” – which the Ministry of Health defines as three doses of the Pfizer, Moderna or Novavax vaccine, or four doses of the Sinovac vaccine – retain long-term protection against severe illness if infected.

Dr Kurup said they may want to have boosters annually, the same way they do for influenza, to “ring-fence” vulnerable family members, or if they do not want to get sick as they plan to travel or are sitting exams, or just to maintain good health.