KUALA LUMPUR, Oct 8 — Malaysia has insufficient local data and studies to prove that Covid-19 booster shots are necessary to maintain protection against the disease, immunologists say.
Today, the National Pharmaceutical Regulatory Agency (NPRA) gave blanket approval for all adults to receive a booster dose with Pfizer-BioNTech’s Covid-19 vaccine at least six months after their second jab.
Malaysia’s first real-world study on Covid-19 vaccine efficacy, the RECoVaM study undertaken from April 1 to September 12, showed that two doses of the Pfizer-BioNTech, AstraZeneca-Oxford, and Sinovac vaccines still protect against severe disease and death, even during the emergence of the Delta variant.
Thus, CodeBlue conducted an exclusive interview with Translational Immunology Group for Education, Research and Society (TIGERS) concerning the need for a mass Covid-19 booster programme in Malaysia.
What is the necessity for a mass Covid-19 booster programme in Malaysia? Overall, hospital and intensive care unit admission rates are seeing a decline across the nation.
Vaccine-induced protection is illustrated via the production of antibodies, as well as the induction of immunologic memory. It is known that circulating antibody levels would usually wane after a primary vaccination below a level required for protection.
Immunologic memory then becomes important in protection against future exposure to that pathogen (i.e. SARS-CoV-2 virus) and this will depend on the incubation period, quality of memory response and subsequent antibody level induced by memory B cells. Thus, to maintain immunity after a full vaccination, a booster dose of a vaccine is essentially given.
However, we are still learning about the Covid-19 vaccines on their length of protection against Covid-19, and especially with the emergence of variants of concern, and thus the need and timing for a booster dose.
In essence, a person fully vaccinated (either one or two doses depending on the type of vaccine administered) would have resulted in a good immune response. This is generally expected for those who are immunocompetent, but how long this protective level of Covid-19 antibody lasts needs to be addressed by local studies, and not simply be based on data from abroad.
Are there sufficient studies conducted in Malaysia to prove the need for a mass Covid-19 booster programme?
There is insufficient information from local studies or insufficient studies on vaccine-induced protection to clearly provide a decision on giving a booster dose. However, looking at recent data from the RECoVaM study (Real-World Evaluation of Covid-19 Vaccines under the Malaysia Immunisation Program), it would seem there is no current priority for a booster dose as the study had shown a decline in the rate of infection, admission to ICU and deaths when individuals are fully vaccinated.
Can waning immunity be the only or primary reason for Malaysia to administer booster Covid-19 shots?
It is normal for virus-derived antibodies (for example, those stimulated by a Covid-19 vaccine) to wane over time. Waning immunity over time is substantiated in many credible papers, but this is over different periods of time depending on the studies.
Currently, there are negligible or incomplete studies in the Malaysian population on antibody testing. But even if they have waned, that does not necessarily mean the body’s capacity to respond to subsequent exposure is gone because we have the immunologic memory of past infections or vaccines. A booster shot that follows the original exposure by vaccination will produce a memory response which is more vigorous than the original exposure.
It is imperative for Malaysia to get its researchers, including clinicians and scientist immunologists, to embark on longitudinal study on immunity amongst cohorts of unvaccinated, partially and fully vaccinated and those post-infection, particularly to decide on the number of doses of vaccine to administer.
What other possible reasons could there be for the resurgence of Covid-19 cases in states which have inoculated 80 per cent of their adult population?
When we say herd immunity (albeit a term that may be less relevant for Covid-19), we refer to the whole country. Reaching the target of 80 per cent of the whole population for state alone is not valid, more of an illusion.
State borders are porous with different phases of the National Recovery Plan and interstate travel will change the demography very quickly. Hence, continuing to observe the standard operating procedures (SOP) is still important to ensure transmission is kept at the minimum.
Other reasons that need consideration include comorbidities, immunocompromised patients, patients with malignancy on immunosuppressive drugs. One also needs to look at the potency of vaccines — for example, is the dosage adequate? This may relate to the emergence of new variants, especially ones that could significantly compromise the effectiveness of the current vaccines.
What factors should be considered or studied before Malaysia administers Covid-19 booster shots?
Factors to consider include whether an individual has been previously infected, having comorbidities and data of local studies on vaccine-induced protection that includes antibody levels with the ability to determined short-term and long-term protection, as well as the immunologic memory of both B-cells and T-cells.
Hence, there will be clear evidence to support the need for a booster dose and the clinical utility would enhance the overall cost-effectiveness of the National Covid-19 Immunisation Programme.
For clarity, as what has been suggested by MOH (the Ministry of Health), the third dose refers to an additional dose for those who would have been more likely deemed not to have mounted an adequate immune response. This will only be prioritised for selected risk groups, such as those who are immunocompromised.
The need for a third dose however, cannot be established without local studies but not discounted at this point in time.
Dr Amir Hamzah Abdul Latiff, Dr Lokman Mohd Noh, Prof Dr Rahim Mohd Noah, Dr Adli Ali, Dr Norazmi Mohd Nor, and Dr Intan Hakimah Ismail, represented TIGERS and took part in this joint interview.
