Through the article "Are we easing movement restrictions a little too soon?" on July 21, EMIR Research warned that a significant portion of the population could have relatively lower antibody levels.
We also mentioned potentially uneven levels of protection due to inoculation with different types of vaccines, which could be unprepared to take on the rising spread of variants, particularly Delta.
Up to Aug 8, only 37.7 per cent of the Klang Valley population have been fully vaccinated, with clear vaccine disparity as nine other states have fully vaccinated populations of well below 25 per cent.
Keep in mind that the protective impact of a certain percentage of a vaccinated population is tied to the effectiveness of the vaccines, as well as the infectivity rate.
Also, a much bigger vaccinated population target may be required prior to phase transitions and easing restrictions.
Further, growing evidence that vaccinated people may also carry and transmit Covid-19 means the traditional herd immunity definition is no longer valid.
Therefore, the future definition appears to be herd immunity against severe infections. But breakthrough infections and future variants could threaten even this outlook.
The Centers for Disease Control and Prevention (CDC) has pointed to published studies indicating Delta to be clearly more infectious and likely to cause more severe disease than Alpha when comparing vaccinated versus unvaccinated groups.
The CDC also referred to studies indicating that for those fully vaccinated, effectiveness in preventing infection and symptomatic disease is lower for Delta compared with Alpha, but similar for hospitalisations and deaths, although this may differ between vaccine types.
Thus, the indicator of the number of patients in severe categories and ICUs may be affected as well, though to a lesser degree than the indicator for daily cases.
The use of such indicators re-emphasises the importance of managing disease progression, whereby large-scale early intervention is key.
Additionally, we should consider other drugs and not put all our options in one vaccine basket.
It was reported that Singaporean researchers using an artificial intelligence platform had identified antiviral drug Remdesivir, together with lopinavir and ritonavir, as the "cocktail" to treat Covid-19 patients with mild to moderate disease and that it has also shown promising results in terms of effectiveness against the Beta and Delta variants.
Malaysia's protocol has already considered these drugs, though Remdesivir is not available here yet. We should speed up and scale up clinical trials (such as for Ivermectin) and other drugs for early intervention, and not wait until we've exhausted all already-approved methods.
Those fully vaccinated in Phase 2 are allowed to make inter-district travel, dine at shops and engage in same-state tourism, as long as they have a digital vaccination certificate.
Though authorities have not recommended antibody measurements, the policy assumes the vaccination certificate is an immunity passport.
We reiterate concerns that in addition to potential differences in the level of protection by vaccines, not all those vaccinated may be immunised and there is risk of waning immunity.
We mentioned before that fully vaccinated people can be carriers, too, especially in the absence of or insufficient mucosal immunity. If they are exposed to non-protected individuals, they could spark sporadic and cluster cases in unprotected communities.
Recent findings by Public Health England and the CDC greatly support this postulation. They found that the PCR cycle-threshold for unvaccinated and vaccinated people is similar, which has been inferred to mean both are carrying similar virus loads and therefore, similar transmissibility.
Consultant paediatrician Datuk Dr Amar-Singh HSS had warned that other states with lower vaccination rates than the Greater Klang Valley may face a Delta outbreak and a potentially worse situation.
We are still firefighting in the Klang Valley. Allowing fully vaccinated people to travel to states with lower vaccination rates is not advisable.
Assuming younger age groups are less likely to show severe symptoms (new variants such as Delta may prove this to be wrong), the minimum consideration for school reopening is a fully vaccinated adult population, which is targeted to be achieved by October.
Younger age groups are not protected, and act as a reservoir for continued transmission and exposure to adults.
We have to be on the side of caution until a higher percentage of vaccinated population is achieved.
The writer is the Head of Science & Technology at EMIR Research, an independent think tank focused on strategic policy recommendations based on rigorous research.