KUALA LUMPUR: With infections spiking and the newer, more transmissible Omicron sub-variant BA.5 on the rise in Malaysia and globally, the Health Ministry Friday warned of a Covid-19 resurgence.
Health minister Khairy Jamaluddin reminded the people to continue practicing public health measures and advised the elderly and those with health conditions to get a second Covid-19 vaccine booster dose.
Is it time for a second booster shot? Who should get it? Should people wait for the new Omicron-specific shots instead?
Experts Epidemiologist Professor Datuk Dr Awang Bulgiba Awang Mahmud of Universiti Malaya; virologist Associate Professor Dr Chee Hui Yee; and molecular virologist Dr Vinod Balasubramaniam spoke to the New Straits Times.
BREAKTHROUGH INFECTIONS
Dr Awang Bulgiba cautioned that Malaysia could be seeing a new wave of Covid-19 infections similar to that of Singapore in two to four weeks' time fuelled by BA.4 and BA.5.
"Their (Singapore) figures are likely a result of more testing as their number of tests per capita is about four times that of Malaysia.
"In the past, despite travel restrictions, waves of infections in both countries have been somewhat similar with one sometimes lagging behind the other.
"With no travel restrictions between the two countries, Malaysia may see a similar wave of infection with a lag of perhaps two to four weeks behind Singapore.
"Rising test positivity rates in Malaysia also point to increasing community transmissions so the true infection rate here is likely higher than reported," he said.
Malaysia recorded 4,020 Covid-19 cases on July 7. According to the health ministry's GitHub database, the last time the country registered over 4,000 cases was on April 24 with 4,006 infections.
The ministry had detected five cases of the BA.5 cases through genomic sequencing up to June 30, but Khairy cautioned that there is a big possibility BA.5 has spread widely in Malaysia.
BA.4 cases have not been detected.
World Health Organisation director-general Tedros Adhanom Ghebreyesus had on June 29 said infections due to BA.4 and BA.5 have contributed to the rise in infections in 110 countries, causing overall global cases to increase by 20 per cent and deaths have risen in three of the six WHO regions.
Dr Vinod of the Jeffrey Cheah School of Medicine and Health Sciences at Monash University Malaysia said alarmingly, even if someone has been infected with the Omicron sub-variant BA.1, re-infection is still possible with sub-lineages of BA.2, BA.4 and BA.5 due to their capacity to evade immune responses.
"Recent data has shown that Omicron sub-variant BA.2.12.1, which has also been detected in Malaysia, is only modestly (1.8-fold) more resistant to sera from vaccinated and boosted individuals than BA.2.
"However, BA.4 and BA.5 is substantially (4.2-fold) more resistant and thus more likely to lead to vaccine breakthrough infections," he explained.
HOW TRANSMISSIBLE ARE THE NEW SUB-VARIANTS?
Dr Vinod shared that a pre-print publication from South Africa suggests BA.4 and BA.5 have a reproduction number (R0) of 18.6.
This, he said is similar to measles, which was until now the most infectious viral disease.
Scientists measure how contagious a disease is by the R0, which is the average number of people an initial case infects in a population with no immunity (from vaccines or previous infection).
"The original Wuhan strain has an R0 of 3.3. Delta has an R0 of 5.1.
"Omicron BA.1 has an R0 of 9.5. BA.2 is 1.4 times more transmissible than BA.1, and so has an R0 of about 13.3," said Dr Vinod.
SEVERITY OF BA.4, BA.5
A recent pre-print publication from a Japanese research group found that in lab-based, cell-culture experiments, BA.4 and BA.5 were able to replicate more efficiently in the lungs than BA.2, Dr Vinod noted.
"In hamster experiments, it developed into a more serious illness. However, data from South Africa and the UK found that their BA.4 and BA.5 wave didn't see a major increase in severe disease and death.
"This is possibly because of the high rates of immunity due to previous infections. Our high rates of vaccine-induced immunity might have a similar protective effect here."
Dr Awang Bulgiba said the two sub-variants, which are also displacing earlier Omicron variants in other countries do not appear to be more virulent.
He added that milder illness may not necessarily be due to the virus being weaker but may point to evidence of long-term population immunity prevailing over the variant.
DO THE ORIGINAL COVID VACCINES PROTECT US AGAINST NEWER VARIANTS?
Dr Awang Bulgiba said there isn't sufficient data to indicate whether current vaccines offer the same effectiveness against BA.4 and BA.5.
Dr Vinod, meanwhile, stressed that vaccines alone will not end this pandemic, in part because of more transmissible new variants and also because vaccines were primarily designed to protect against severe disease and death.
WHY SHOULD I GET BOOSTED NOW THEN?
Vaccines are more than just about inducing the body to produce antibodies as they also induce cellular immunity which works in a different way and help prevent more severe disease, Dr Awang Bulgiba said.
He explained that as antibody levels induced by vaccines will likely wane over time, a vaccinated person can still be infected.
However, Dr Awang Bulgiba said if the person's body can still mount an immune response because there are sufficient memory B- and T-cells, then the possibility of severe disease is lessened.
"The United Kingdom, Portugal and South Africa have seen quite a number of infections caused by BA.4 and BA.5 but severe disease rates and hospitalisations remain within manageable limits in those countries.
"The infection rates in Portugal have come down without the benefit of the newer bivalent vaccines, indicating that protection against severe disease remained strong with the monovalent vaccines.
"Hopefully, the rate of severe disease and hospitalisation in Malaysia will not be higher with BA.4 and BA.5 compared to BA.1."
WHO SHOULD GET THE SECOND BOOSTER JAB?
Dr Chee said high risk individuals can consider taking the second booster now to prevent severe illness and the risk of being hospitalised due to waning immunity.
Dr Vinod said although existing vaccines provide some protection against serious illness and death, chances of reinfection are high with the current BA.4 and BA.5.
Therefore, he said it is pertinent for the vulnerable group to get their second booster shots.
"We might experience mild to moderate symptoms, especially for those who are in the vulnerable group (elderly above 60, individuals with comorbidities, children, and the immunocompromised).
"While infections are starting to show an increase in Malaysia, the mortality rate is not as high as the time when the Delta variant was at its peak.
Dr Vinod added that if BA.4. and BA.5 continue to surge, there is a chance that others might also need second booster doses to reduce the burden in hospitals, especially with waning immunity for those who received their booster doses past six months.
"As of now, our hospitals are still coping and there is no urgent need to postpone elective surgeries as some quarters of the community worry and there is no need to re-introduce lockdowns similar to previous years."
WHY SHOULD OTHERS WAIT FOR THE OMICRON-SPECIFIC SHOTS?
Dr Chee said research has shown that Omicron-specific vaccines or bivalent boosters have elicited strong antibody response against extremely contagious sub-variants.
Bivalent booster is a vaccine that includes both the original coronavirus strain and the new strain, in this case, the BA.4/5 spike protein component.
"If you do not have risk factors for severe diseases and are not immunocompromised, and you have had your first booster jab, then there is no need to rush for a second booster now.
"With Omicron and its sub-variants becoming dominant, it is wise for healthy adults to wait for an Omicron-specific vaccine.
"Covid-19 will eventually become like the flu, where a shot needs to be taken every year to prevent different virus strains," she said.
The European Medicines Agency (EMA) had on July 1 said an Omicron-specific vaccine could "increase and extend" protection when used as a booster.
The statement refers specifically to the mRNA vaccines. Pfizer-BioNTech and Moderna have both got newer bivalent vaccines which have undergone clinical trials.
On July 6, two vaccines - Pfizer and Moderna - that specifically target the Omicron variant have been granted "provisional determination" by Australia's drugs regulator, the first step for getting full approval for its use.
Dr Awang Bulgiba, however, noted that these were created with BA.1 in mind hence it is uncertain whether they will offer the same protection against BA.4 and BA.5.
"It is perhaps why the United States Food and Drug Administration (FDA) wants to include vaccines designed with BA.4 and BA.5 in mind as boosters for the coming fall in the US."
The FDA had in June recommended that vaccine companies update their booster shots to target BA.4 and BA.5 that are driving up cases in a number of countries.
CONTINUE COVID-19 SAFETY MEASURES
Dr Awang Bulgiba stressed that in addition to vaccination (primary series plus booster), non-pharmaceutical interventions or NPIs remain critical in protecting against the Covid-19 virus especially with the Omicron sub-variants.
Thus, he said people should continue to observe the safety guidelines, including wearing masks, having good hand hygiene, and avoiding crowded spaces, rather than just depend on vaccination to avoid severe disease.
"This is particularly true in indoor environments where ventilation may not be as good. Unfortunately, there are people who simply refuse to mask up even during indoor public events and in crowded places.
"It is thus likely that we will see a rising number of new infections with these sub-variants."
He said at present, protection against severe Covid-19 disease remains strong with the current monovalent vaccines and most adults have had boosters in Malaysia.
WILL PEOPLE REQUIRE AN ANNUAL SHOT AGAINST COVID?
Dr Awang Bulgiba further said repeated boosting with the same type of vaccine is not a sustainable public health strategy.
"Unless there is strong evidence for the need, I doubt if the uptake will be good enough to warrant second boosters for the general population for the moment.
"If more boosters are required, the authorities should start thinking of bivalent vaccines rather than the current monovalent ones.
"Otherwise, we will risk having to ask people to boost again in a few months' time if a new variant emerges."
He noted that in the future, pan-coronavirus vaccines and vaccines which are specifically designed to induce cellular immunity will probably be required.
Dr Awang Bulgiba pointed out that the narrative around vaccine effectiveness was set at the beginning of the very first Covid-19 vaccine trials to be the prevention of symptomatic infection.
This, he said has set the tone for all analyses of vaccine effectiveness, which has led to repeated boosters with short-lasting effectiveness as this is simply based on prevention of symptomatic infection.
"I have repeatedly called on the health authorities to think of a permanent structure for Covid-19 vaccination if repeated boosters prove to be necessary. Right now, the thinking is still ad hoc but the planning for such vaccination should already be made.
"In the future, pan-coronavirus vaccines may be a permanent part of the National Immunisation Programme, so the planning needs to be done now."
Dr Vinod, meanwhile, said by the looks of how well the virus has adapted to humans especially from vaccines-induced immune selection pressure, it definitively looks like the virus is here to stay and people have to adapt accordingly.