Covid-19 vaccine booster shots will likely be required to ensure the population remains protected against the virus and any new or more contagious variants.
Epidemiologist Professor Datuk Dr Awang Bulgiba Awang Mahmud said if booster jabs were required, then the Covid-19 National Immunisation Programme would need to continue beyond its original time frame.
He said more resources had to be made available and the establishment of a more permanent structure.
"Currently, there is no consensus on this although there have been suggestions that booster jabs will be needed in time. It will depend on the vaccines administered to the recipients," he told the New Straits Times.
The Science, Technology and Innovation Ministry's Covid-19 Epidemiological Analysis and Strategies Task Force chairman said the different and emerging Covid-19 variants might affect the course of the pandemic, depending on the implementation of the vaccination programme.
He said that while newer variants would have fewer opportunities to take root with high vaccination coverage, detection of more cases involving variants of concern (VOCs) could prolong the pandemic.
"A VOC may spread faster, stay longer in the host, escape antibodies and be harder to diagnose and harder to treat.
"It should be considered as being potentially more dangerous and more difficult to control. If a VOC is harder to detect and more transmissible, then it will make it more difficult for us to end this pandemic."
So far, the VOCs found in Malaysia are the United Kingdom (UK) variant (B.1.1.7), South Africa variant (B.1.351) and the India variant (B.1.617).
The implications of a VOC, he said were stricter precautions like double masking, use of N95 face masks, lengthier quarantine and isolation period, use of alternative or more sophisticated diagnostic kits, different vaccines, and treatments.
Dr Awang Bulgiba said there were thousands of SARS-Cov2 virus mutations, and a variant could have several mutations.
B.1.1.7, he said, had multiple mutations, with the two most significant being N501Y, which affects the spike protein, hence potentially its infectiousness, and the 69-70 deletion, whose effect is unclear.
B.1.351 has multiple mutations, which include N501Y and E484K, which affect the spike protein and might have influence the infectiousness, he said.
On whether the current vaccines could work against these variants, he said in a laboratory setting, vaccines from Western countries appeared to be effective against them, although the number of neutralising antibodies in response to newer variants varied.
"One variable that has to be considered is not just antibodies but T-cells.
"Although largely unknown, it is likely that T-cells induced by vaccines will remain and may prove just as vital in the battle against these variants.
"Recent reports (not yet peer-reviewed) suggest that the number of antibodies in response to B.1.351 through immunisation by the vaccines currently in use is fewer than that for other variants, but they suggest that the vaccines may still work via other mechanisms.
"The vaccines being used in the UK work against B.1.1.7, and a recent report (not yet peer-reviewed) suggests that the Pfizer BioNTech vaccine works against B.1.351 to some extent despite the presence of the N484K mutation, which is said to enable the virus to evade antibodies."
He said the efficacy of vaccines depended on factors, such as the prevalent variants, compliance with dosing schedules, level of humoral and cellular immunity and whether non-pharmaceutical interventions were continued in tandem with vaccinations.
The Independent Covid-19 Vaccination Advisory Committee, said Dr Awang Bulgiba, had recommended to the government the establishment of a Voluntary Covid-19 Vaccination Registry where 50,000 vaccinees would be recruited as volunteers and monitored for two years.
He said this was to study and evaluate how long the immunity from the vaccination from different vaccines could last, so B-cells and T-cells testings must be conducted in addition to antibody levels.
"Rare side effects can be monitored this way.
"We can study whether mixing vaccines result in a better immune response than relying on a single vaccine type. We hope that the government will heed this call as these B-cells and T-cells are crucial for long-term immunity.
"It is imperative that the government has good surveillance (including genomic surveillance)."
Universiti Putra Malaysia Microbiology Unit head and virologist Associate Professor Dr Chee Hui Yee said a booster in the form of a new vaccine was required if the current vaccines could not provide sufficient protection against Covid-19.
"We can still continue the immunisation programme while waiting for new research (data) on the efficacy of the current vaccine against the VOCs."
Dr Chee said, for now, the vaccines still worked against these variants with different percentages of protection.
If the nation achieved herd immunity sooner, she said it would prevent the virus from spreading and mutating further.
"The more people the virus infects, the greater the number of mutants it will spawn."
"This is a race against time."