SINGAPORE – It is hard to have a long-term vaccination strategy to deal with Covid-19 as the virus is unstable and constantly mutating, with an unknown seasonal pattern and unknown ways of interacting with other respiratory germs.
As the number of severe cases of the coronavirus declines, it will also become increasingly difficult to evaluate the effectiveness of vaccines against such infections in the future.
National Centre for Infectious Diseases (NCID) executive director Vernon Lee said this on Wednesday at the first Asia-Pacific Immunisation Coalition and Asia Dengue Voice and Action Summit on Infectious Diseases and Immunisation.
He was addressing more than 230 participants from 15 countries, comprising mostly healthcare professionals, policymakers, researchers and public health leaders, on the second day of the two-day summit, held at Orchard Hotel Singapore.
Giving an update on the Covid-19 vaccination situation in Singapore, he said: “As of a couple of months back, we see that many doses of vaccines had been administered to our population of less than six million people, and more than 90 per cent of the entire population completed their primary series and 80 per cent have completed what we call minimum protection with at least one additional dose.”
Despite the good results, Professor Lee said mutation of the virus continues, and it is not known if it will continue to evolve in a stable manner.
“So what does this mean for our seasonal co-infections? Do we need an annual vaccine and what is the longevity of this protection?” he said.
To address such co-infections, biopharmaceutical companies are developing a two-in-one messenger RNA (mRNA) vaccine against both Covid-19 and influenza.
mRNA in a vaccine “teaches” cells how to make copies of the spike protein on the viruses in question, so that the body can recognise the real viruses if exposed to them, and fight them.
Moderna used its version on its first participant in a phase three clinical trial on Oct 24, while rival Pfizer announced on Oct 26 that its combination vaccine will be moving into a final-stage trial in the coming months.
Both companies are a step closer to potentially getting regulatory approval for a combination shot for Covid-19 and the flu.
Professor Tikki Pangestu, a visiting professor at the National University of Singapore Yong Loo Lin School of Medicine, said he is sure there will be “no shortcuts from an ethical (or) a regulatory point of view”.
“Regardless of when they announced the clinical trials, HSA (Health Sciences Authority) is never, ever going to approve these two new vaccines for use unless they have seen the data (that) covers safety as well as efficacy,” he told reporters at the summit.
“However, I’m not saying that there is absolutely no risk. Any new vaccine, even after HSA has approved (it), is always going to see some rare side effects or adverse reactions. You can’t predict that until it is used on a lot of people.
“(After all), the clinical trial is a controlled environment with maybe 20, 30 or 40,000 subjects,” he said.
Reflecting on Singapore’s management of the pandemic so far, Prof Lee said placing its bets early on vaccines to protect its people against Covid-19 and other infectious diseases gave the country a leg-up in having a highly resilient community.
He added that a lot of the social measures that were put in place during the pandemic – such as not allowing those who were unvaccinated to enter shopping malls or to eat out at restaurants – also influenced people’s choice on vaccination.
“Back in the day, we had no idea which vaccine would be the most effective, so we wanted to hedge our bets on the different classes of vaccines and all these vaccines have proven to be effective, some slightly more effective than others,” he said, adding that the decision had been the right one.
