Higher protection from Moderna booster for those above 60 who took Pfizer earlier: NCID
SINGAPORE — A Moderna booster shot provides significantly better protection against COVID-19 for those above 60 years old who had taken Pfizer jabs, compared with a third Pfizer dose.
After seven days, the average antibody level among those who had a Moderna booster was about twice as high as those who were administered a Pfizer dose, according to researchers at the National Centre for Infectious Diseases (NCID).
The findings – announced in a press release on Thursday (17 March) – also show that 28 days after a booster, average antibody levels in those above 60 were 84.3 per cent for those who had taken the Moderna booster, compared with 72.8 per cent for Pfizer.
The outcomes were consistent across all COVID-19 variants of concern, from Alpha to Omicron, the study added.
However, antibody levels were similar in younger adults regardless of whether they had received a Moderna or Pfizer booster.
Lead researcher Dr Barnaby Young, who is the head of the NCID's Singapore Infectious Disease Clinical Research Network, said having a higher antibody level is likely to offer greater protection against Omicron.
"Taking Moderna as a booster shot may offer better or longer protection for older adults as well, as our research has observed a higher anti-spike antibody titer and a stronger neutralising response of the vaccine against the Omicron variant," he added.
The study also found that adverse vaccine reactions, while common, were mild and short-lived. Such common reactions include pain at the injection site within 72 hours of a booster, and muscle pain arising from fatigue.
For those 60 and above, fever and weakness occurred more frequently among who had received a Moderna booster dose. No participant had experienced any serious side effect, the study showed.
These observations complement other international trials and provide "reassuring" local data that a third dose of mRNA vaccine is safe and effective at boosting the immune response, the NCID said.
The study, conducted between 12 October and 3 December last year, involved 100 participants who had received the Pfizer shots as their primary series of COVID-19 vaccination. Of them, half were above 60 years old.
The study, which is yet to be peer-reviewed, was published on Thursday in the research repository SSRN.
The participants were randomly assigned to receive either a Moderna or Pfizer booster shot. Blood samples were collected 28 days before the booster as well as seven and 28 days after the shot.
The study will continue to follow participants and monitor the waning of antibody levels after their booster shots, with additional blood samples to be collected after six months and one year, the NCID said.
The current phase of the study, which started on 3 January, will cover up to 200 participants who had earlier received either the Pfizer or Moderna shots as their primary series. They will be randomly allocated to receive either Pfizer, Moderna, as well as Covaxin booster shots.
The NCID said that it plans to extend the study to other vaccines, including Nuvaxovid, and could involve up to 600 participants ranging across ages and ethnicities.
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