Additional booster shots

The Singapore population currently has some degree of resistance against Covid-19, thanks to high levels of infections and the recent administration of booster vaccinations, but this will not remain the case indefinitely, infectious diseases expert Teo Yik Ying said yesterday.

Professor Teo, who is dean of the National University of Singapore’s Saw Swee Hock School of Public Health, said people may need multiple boosters, perhaps taken annually, or the country may see another outbreak or recurrent waves of Covid-19 in the future.

National Centre for Infectious Diseases executive director Leo Yee Sin added that the authorities are looking closely at the local data before making a decision, noting that many countries now offer additional shots for those over the age of 80.

Flu and other diseases

Even though Covid-19 has killed more than 1,100 people in Singapore, some deaths from other causes might have been prevented due to the reduction in social interactions.

Professor Leo noted that Singapore was among a handful of countries and regions that saw a negative excess mortality rate in 2020 and last year, according to a study published in The Lancet medical journal.

This means that fewer people died overall during the pandemic compared with the years before.

Professor Dale Fisher, a senior infectious diseases consultant at the National University Hospital, said that while cases of diseases such as hand, foot and mouth and even sexually transmitted infections would have declined because of the lower level of social interaction, other negative factors such as childhood weight gain and mental health issues are on the rise.

Prof Teo said the impact of the measures themselves may prove to be just as significant as Covid-19.

Herd immunity

Prof Teo said that getting vaccinated or being exposed to the coronavirus provides immunological protection so that subsequent exposures will not be as severe.

He also noted that the currently dominant Omicron variant is less severe than the Delta variant, and questioned whether it might be the right time to allow people to be exposed to the virus naturally and build up their immunity.

In the years to come, Covid-19 may hit in “returning waves”, but each wave may cause fewer and fewer severe illnesses as people’s bodies get used to it, he added.

Prof Leo, however, cautioned against taking Omicron too lightly. She noted that Omicron is effective at evading the immune system, even if one has been previously infected by Delta or another strain.

The Deltacron variant

One recent development is the so-called Deltacron variant, which combines the characteristics of the Delta and Omicron variants, but little is currently known about it, said Prof Leo.

“Although the number is very small at this point in time, it may fizzle out or it may become a problem,” she said.

“We just don’t know.”

Prof Leo added that it is possible that yet another variant could emerge, even as scientists are busy studying the Deltacron variant, which was first detected in Covid-19 samples collected from France in January.

According to Gisaid, an online open-access repository for genomic data on viruses, 35 cases have been detected in France and eight in Denmark. Germany, Belgium and the

Netherlands each have one case, while genetic sequencing company Helix has identified two cases in the United States.

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