Vaccines still key in curbing COVID amid Omicron BA.2.75 cases: Singapore experts

COVID-19 vaccines remain broadly effective in reducing the severity of diseases and hospitalisation rates, even as they become less effective against the new Omicron BA.2.75 subvariant, said Singapore experts. (Reuters file photo)
COVID-19 vaccines remain broadly effective in reducing the severity of diseases and hospitalisation rates, even as they become less effective against the new Omicron BA.2.75 subvariant, said Singapore experts. (Reuters file photo)

SINGAPORE — COVID-19 vaccines remain broadly effective in reducing the severity of diseases and hospitalisation rates, even as they become less effective against the new Omicron BA.2.75 subvariant, said medical experts in Singapore.

The BA.2.75 strain, unofficially dubbed “Centaurus”, was first detected in India in May. Over 200 cases of the Omicron subvariant have been detected in over 10 other countries including Singapore, the US, Australia, Canada, as well as the UK where such cases have sharply risen.

In Singapore, at least six such local cases and two imported cases, who had travelled to India, have been detected. Authorities said all local cases had mild symptoms.

The World Health Organization (WHO) has designated BA.2.75, relative to BA.1 and BA.2, as an Omicron subvariant under monitoring, although its chief scientist, Dr Soumya Swaminathan, said there were not enough samples globally as yet to assess its severity.

Currently, the BA.5 and BA.4 subvariants are rapidly displacing the previously dominant BA.2 subvariant in many countries, including Singapore. The city-state is currently facing a wave of infections driven by both BA.5 and BA.4, but there are indications in early July that it is near or at its peak.

But there are fears that BA.2.75 may quickly overtake BA.5 and BA.4 as it has more unique mutations on the spike gene that have not been observed in other variants.

Too early to assess BA.2.75 subvariant's impact

The surge in the number of infections with BA.2.75 suggests that the COVID-19 virus continues to evolve to replace older lineages, said Yvonne Su, an associate professor at the Duke-National University of Singapore (Duke-NUS) Medical School's programme in Emerging Infectious Diseases.

But it is still too early to predict the effect of these mutations, said Prof Su, noting that it is not just the exact mutations that matter, but also the combination that can affect virus characteristics.

"It is therefore important to determine if BA.2.75 infection leads to increased virulence and more severe disease, especially in vulnerable groups such as the elderly but also infants and toddlers as they are still largely unvaccinated," she added, in response to queries from Yahoo News Singapore.

But experts said that while there will be more cases of infections due to evolving, new Omicron variants, there are likely to be fewer fatalities, in line with observations of COVID-19 figures around the globe.

This has happened with the BA.4 and BA.5 subvariants, which are more infectious because they could resist some of the immune response, said Professor Dale Fisher, who is on the WHO's Global Outbreak Alert and Response Network.

While they have caused more cases, there was no increase in the rate of severe diseases, added the senior consultant at National University Hospital’s Division of Infectious Diseases.

Infectious diseases expert Paul Tambyah, who drew parallels to the deadly 1918 Spanish flu pandemic, said that later variants of viruses tend to be more transmissible and less virulent.

"The vaccines currently in use target the original strain (originating from Wuhan in China) and thus, are expected to be less effective against newer variants than the original strains," he said.

"There will be more cases until there are few left in Singapore uninfected but there will definitely be fewer fatalities. This is in line with what has been seen all over the world."

Vaccination in S'pore to be extended to children aged 6 months to 4 years old

At 94 per cent, most of Singapore's total population have completed their full vaccination regimen while 79 per cent have received a booster shot. Those aged between 50 and 80 and above are allowed to get a second vaccine booster.

Under the national vaccination programme in Singapore, COVID-19 vaccines are offered to those aged five and above. However, those below 18 must have the consent of their parents or guardians to receive their vaccination and can only be vaccinated with the Pfizer-BioNTech/Comirnaty vaccine.

Those aged five to 11 are given a smaller dose of the Pfizer vaccine, developed using messenger ribonucleic acid (mRNA) technology, compared with adolescents and adults. Those aged 12 to 17 can only get the Pfizer vaccine.

For those aged 18 and above, apart from Pfizer, they can also choose from Novavax's protein-based Nuvaxovid, the inactivated CoronaVac developed by Chinese vaccine maker Sinovac and Moderna's MrNA Spikevax.

The Ministry of Health (MOH), in response to media queries on Monday (25 July), said it is currently doing the necessary preparation to roll out COVID-19 vaccines for young children aged between 6 months and four years, and aims to have the processes ready towards the fourth quarter of the year.

MOH did not specify which vaccines would be available for this age group.

The announcement comes after two children, aged 1.5 and four, recently died from COVID-19 in Singapore within the last four weeks – the only two fatalities caused by the coronavirus aged below 12 here.

Of the 1.7 million COVID-19 cases reported in Singapore since the start of the pandemic, about 64,000, or 3.9 per cent, were children aged under five, said MOH.The large majority of the 64,000 cases recover uneventfully at home, with 0.022 per cent requiring oxygen supplementation or intensive care unit (ICU) care.

In comparison, 0.17 per cent of patients in the 40 and above age group require ICU care, MOH noted.

"The incidence rate of ICU care amongst the 5 to 39 group is almost negligible," it added.

MOH also noted that the two deaths of the children translate to three deaths per 100,000 cases in the same age group, compared with 99 deaths per 100,000 cases for the 40 and above age group this year.

"This is not unique to COVID-19 as we see such patterns in other infectious diseases, where children 0 to 4 are much more resilient than older patients, but more vulnerable compared to older children and young adults," it added.

Before COVID-19, in 2018 and 2019, MOH recorded 3.1 deaths of children aged 0 to 4 years old per 100,000 person-years from pneumonia and influenza. Figures for 2018 and 2019 were used as a comparison as public health measures rolled out during the COVID-19 pandemic have significantly reduced the numbers for pneumonia and influenza, it added.

"There is currently no clear evidence that Omicron variants cause more severe disease. Severe cases among those aged 0 to 4 have been lower at 12 per 100,000 cases in 2022 compared to 41 per 100,000 cases in 2021," MOH said.

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