Covid-19 vaccine protection wanes faster among the elderly, booster shots needed: NUS study

SINGAPORE - Senior citizens should consider receiving booster doses of the updated Covid-19 vaccine regularly, according to a recently published study by local researchers.

This is because in people over 65, protection from the first two doses wanes faster as they have a lower immune cell count.

The study was led by Dr Vanda Ho, a PhD student at the Department of Microbiology and Immunology, and Immunology and Infectious Diseases Translational Research Programmes at NUS Yong Loo Lin School of Medicine.

It involved 29 participants, 14 of whom were aged between 66 and 82, and the rest being younger adults between 25 and 39 years old. They all received two doses of Pfizer’s mRNA Covid-19 vaccine.

The findings of the study were published in the peer-reviewed journal Ageing Cell in February.

“Older adults had a significant increase in neutralisation after the second dose, but this was still lower than the younger adults, despite the former being robust,” said Dr Ho.

So it is important for older adults to go for booster vaccinations regularly to protect themselves, she noted.

mRNA vaccines work by introducing a small piece of a protein found in the virus so that cells can produce the viral protein. The immune system then recognises the protein as foreign and produces antibodies to protect the body against infection. 

The immune system can be triggered by a vaccine to produce neutralising antibodies in response to the virus or bacteria in the vaccine, resulting in the system recognising and fighting the infection naturally when exposed to the disease later.

As a geriatrician at the National University Hospital, Dr Ho often sees older adults come into the wards with infections for the first time.

“Unfortunately, after that first infection, they tend to be re-admitted for further infections. I saw the same patients decline functionally and cognitively because of the initial infection.

“That really triggered my interest – that maybe we can prevent the infection, or at least reduce the side effects, then we can help to increase their health span,” she told The Straits Times.

She added that just as she was thinking of conducting research on the topic as part of her doctoral studies, “the Covid-19 pandemic hit, and it turned out to be a blessing in disguise”.

“It was really a great opportunity to capitalise on,” she said.

“Everyone in the world was getting the same immune stimulus: the Covid-19 vaccination. Prior to that, older and younger adults went through different vaccination regimens. The pandemic presented us with the best opportunity to study if pre- and post-vaccinated older and younger adults respond the same way.