askST: Do current Covid-19 measures work for B1617 strain? Is Pfizer vaccine safe for teens?

Pfizer said children in the clinical trial group had robust antibody responses and that the vaccine was 100 per cent effective.
Pfizer said children in the clinical trial group had robust antibody responses and that the vaccine was 100 per cent effective.PHOTO: ST FILE

SINGAPORE - As Singapore tightens measures amid a rise in cases and the ongoing battle to contain a more virulent B1617 strain, The Straits Times answers some questions, from mask wearing to vaccine safety for teens.

Q: Has the B1617 strain been the driver of new infections in schools and other clusters and rendered old measures ineffective?

A: Existing measures such as mask wearing and safe distancing have been effective, but the new B1617 variant will expose the smallest breaches that people here would have got away with in the past, Professor Dale Fisher, an infectious disease expert from the National University of Singapore Yong Loo Lin School of Medicine, said. The variant, which initial studies have shown to be more transmissible, has contributed to the current surge of cases in India.

Scientists in Britain have estimated the B1617 variant as being 70 per cent more transmissible than the B117 variant, which originated in Britain.

Associate Professor Hsu Li Yang said it will be hard to avoid new cases in the long run. And even more so when more transmissible variants emerge, added the vice-dean of global health at NUS Saw Swee Hock School of Public Health.

This means that Singapore needs to modify its measures as more data on the virus and its variants emerges, be it for public spaces, the workplace or steps individuals must take, such as wearing a mask with high filtration capability.

Q: In the latest guidelines, masks with high filtration capability should be worn. Since surgical masks meet this criterion, why do front-facing healthcare workers need to wear an N95 mask? Do we need to wear an N95 mask as well to prevent airborne transmission?

A: It is generally accepted that airborne transmission can happen, especially in hospitals, where aerosols are used and where there are more instances of people coughing and sneezing.

But for the vast majority of cases, the virus spreads through droplets. Hence, conventional surgical masks will continue to serve us well. There are exceptions, of course, such as in a poorly ventilated area, where aerosols that contain the virus are more likely to spread infection.

The Ministry of Health (MOH) has recently introduced N95 masks in hospitals and that has generated some discussion. It is important to realise that the stakes are high in hospitals as it is a setting where there are vulnerable patients, some of whom may not be wearing any masks, and social distancing is not always possible.

MOH will hence want to take additional precautions to protect these hospitals and be more risk averse.

If aerosol transmission was possible in the past, it may be more likely now. To fight that, it is important that places have good ventilation, such as by keeping windows open to allow for good airflow.

Q: Is the Pfizer jab safe for those aged between 12 and 16?

A: It is important to highlight Pfizer's study of about 2,200 children aged 12 to 15 in the United States. In the trial, 18 cases of Covid-19 were observed in the placebo group, which consisted of around 1,100 children, versus no cases of Covid-19 in the vaccinated group, which also had around 1,100 children.

Pfizer said the children in this group had robust antibody responses and that the vaccine was 100 per cent effective.

The trial also showed that the vaccine was safe for that group. The jab was well tolerated, with side effects generally consistent with those observed in trial participants from the 16 to 25 age group.