COVID-19 Update: Herd Immunity, Children's Vaccines, Booster Doses, and New Treatments

In today's column, I wish to broach the intertwining issues of herd immunity, booster doses, children's vaccines, and new treatments for COVID-19.


(Representational Image: Unsplash)

The most transmissible SARS-CoV-2 delta variant has become the dominant strain globally, having spread to over 100 countries worldwide. The number of Covid cases globally now stands at 192.5 million, with over 4.12 million deaths worldwide. Several countries are now facing a fresh COVID surge and are imposing lockdowns and other control measures to contain the spread. These include Indonesia, US, Australia, Brazil, Israel, UK, Spain, Turkey, Philippines and parts of Africa.

What’s herd immunity?

The further spread of COVID-19 can only be stopped if we achieve herd immunity through natural infections and/or vaccinations. What's herd immunity? This means that enough population has developed immunity through infections or vaccinations, so that there is no further transmission from them to the unvaccinated population. What's the reasonable threshold for achieving this herd immunity?

There are several viewpoints regarding this. Earlier, we thought that 70 per cent may be a good threshold for achieving herd immunity. But this depends, among other things, on the infectiousness (R value) of the virus and the efficiency of the vaccine. Now, it seems with the global spread of delta variant, the 70% threshold doesn't hold any more.  Unfortunately, delta's R value seems quite high while the effectiveness of most vaccines is very low against the delta strain. Under these conditions, it seems we need to vaccinate much larger ratio of the population to achieve herd immunity. According to several reports, it's quite probable that about 90% of the population needs to be vaccinated to achieve this desirable endpoint (The Irish Times, July 23, 2021; Connexion France, July 24, 2021).

According to the United States CDC, is a very attractive mirage that is not attained usually. It says that herd immunity on a global scale was reached only once, with the eradication of the smallpox in 1980 (The Conversation, May 14, 2021). We're also about to achieve global herd immunity for polio. It seems that herd immunity is a rare thing and can only be achieved worldwide in a few instances, only through extraordinary efforts and global collaboration. Under the current pace of vaccinations in many poor countries and the level of global cooperation as well as people's behaviour and many government's response, herd immunity against Covid-19 seems long way off.

The only feasible option is to vaccinate as many people as possible at the quickest time and prevent hospitalizations and deaths, if not infections altogether. In addition, the common people can help ward off the hard impacts of the coronavirus by adhering strictly to Covid-appropriate behaviour.

CDC highlights two factors that may impede the crossing of the herd immunity threshold. One if "vaccine hesitancy" i.e. a significant fraction of the adult population refusing to take the vaccine and the other if the possible need to vaccinate adolescents and children. Obviously, children (age 18 and less) need to be quickly vaccinated for their own sake and also for the sake of achieving herd immunity. Would it be possible in the near future, when the majority of the adults are yet to be vaccinated in many poor nations?

Children's vaccines

The leading science journal Nature has analyzed the need for vaccinating children in a recent paper (Nature, July 24, 2021). On July 19, the UK government recommended delaying vaccines for young persons under 16, as there are very low rates of serious disease in this age category. However several countries, including US and Israel, have gone ahead and vaccinated children with approved pediatric vaccines thay have currently. Other countries are also lining up to vaccinate their young people as soon as vaccines become available.

The matter is rather complex arising from the interplay of many factors. Though children are at low risk, some children do get seriously ill and some even develop post-Covid complications such as MIS-C. In some countries, the proportion of children who got serious infections or who died from COVID-19 is not known, leading to confusion about the need to vaccinate them. Another point is vaccine availability. Only a handful of vaccines for young people over the age of 12 are available, e.g. Moderna and Pfizer vaccines in US; and Sinovac and Sinopharm in China. Another factor that muddles the issue is the question of safety. Though vaccines seems to be safe for young persons, a potential link between the Pfizer vaccine and inflammation of the heart (myocarditis and pericarditis) has been reported.

No vaccine has been approved for children in India. But trials are on and, at least, two vaccines: Zydus Cadila and Bharat Biotech, are expected to be available by September/October 2021.

Booster doses

An Israeli study has reported the waning of Pfizer vaccine's efficacy from 95% (Jan.-April, 2021) to 39% (June-July, 2021) and indicated the possible need for a booster dose (third jab). Earlier, the vaccine's efficacy in preventing infections was quite high (95%) but now has waned to very low levels (just 39%). However, the heartening data is that its efficacy in preventing serious disease remains high (about 91.4%) (The Print, July 24, 2021).

So, is there a need for administering a booster shot to those who have received a 2nd shot of a vaccine? However, scientists have warned that without more careful analysis of data, it would be still premature to recommend a booster vaccine.

However, no vaccine is 100% efficient. And the immunity triggered by many vaccines is not long-lived. The spread of variants such as delta poses a challenge to the currently available vaccines. Soon, a booster jab may be required not only in Israel but also in many other countries. At least, it may be needed in certain sections of the adult population such as the elderly and those with co-morbidities.

New treatments

As vaccinating the global population will take a long time and as vaccines are not 100% effective in preventing infections, there's the urgent need for drugs or pills that can slow down the Coronavirus or inhibit its replication, if not curing it altogether. However, the teratment protocol for COVID-19 keeps changing. Drugs which used to be highly popular in the early stage of the pandemic e.g. hydroxychloroquine and ivermectin have now been drooped from the list of medications. At the same time, some new treatments have been suggested recently.

On July 6, the WHO approved two rheumatoid arthritis drugs-tocilizumab and sarilumab-for COVID-19 (The Scroll, July 24, 2021).

Tocilizumab is an interleukin-6 (IL-6) blocker and is recommended for serious patients fighting lung infections by the coronavirus. In the advanced stage of COVID-19, some people develop severe inflammation in lungs and other organs due to the so-called "cytokine storm", in which the body releases IL-6 cytokines in excessive levels, causing inflammation leading to breathing difficulties and other complications. Tocilizumab blocks the effects of IL-6 and helps "tame" the cytokine storm. However, there's also the danger that while trying to lull the body's immune system, the patients may develop secondary bacterial and fungal infections due to the weakened immune system. This drug is imported by Cipla in India, and costs about Rs. 32,480 (per 400 mg vial, as of July 21, 2021). Other drugs recently approved in India are REGEN-COV-2 (cocktail of 2 monoclonal antibodies), made by Roche company and 2-deoxy-D-glucose (2-DG), developed by DRDO, Govt. of India.

Other drugs in the pipeline include the antiviral molunupiravir from Merck Company and masitinib (which inhibits replication of SARS-CoV-2 coronavirus), being studies at the University of Chicago, US (The Mint, July 22, 2021). Another promising post-infection treatment for COVID-19 is the protease inhibitor,GC376, that blocks the activation of proteins needed for the production of infectious viral particles, and, thus, inhibits the viral reproduction and transmission (India Today, July 5, 2021). We need to wait for successful clinical trails of these new drugs before they land up in the market and in clinics and hospital beds of Covid patients.

Possible measures for Manipur

We need to assume that there may be a third wave in Manipur too. Even if that may turn out to be a wrong anticipation, it's better to err on the side of caution. Accordingly, we must initiate measures to squarely face a possible third wave in our state. These may include:

Speeding up vaccinations in a big way.

Genomic sequencing of a subset of positive cases and surveillance of the variants including the delta variant: which COVID strains are there in Manipur, where are they, and where are they moving towards.

Boosting up healthcare provisions such as medical oxygen plants, tankers and cylinders; steroids, antifungal drugs, oxygen concentrators, ventilators, oximeters, masks, PPEs, sanitizers etc.

Strengthening of healthcare infrastructure such as construction of new COVID hospitals.

Provision of more COVID care centres (CCCs), more Covid beds and ICUs in existing hospitals

Constitution of a special taskforce for the third wave; a separate taskforce for pediatric COVID is also highly recommended.

Special provisions for kids such as pediatric hospitals, wards, and ICUs, pediatric oximeters, concentrators, and ventilators and strengthening of staff such as pediatricians and pediatric nurses and paramedical workers etc.

As an editorial in the prestigious medical journal, The Lancet Microbe (Jan. 1, 2021) says, "Vaccines will be instrumental in the control of COVID-19, but their global distribution will be challenging and their effect won't be immediate." So, in the meantime, we must not let our guards down and we must still strictly observe the non-pharmaceutical interventions such as the major SOPs of the use of face masks, physical distancing, and hand hygiene and avoidance of 3 Cs: crowded places, close contact settings, and closed spaces (with poor ventilation). We must religiously follow the protocol of 'test, track, and treat' for months to come. If possible, the public health authorities must take steps to prevent large gatherings such as weddings and death ceremonies, music concerts, and large meetings. The 'hoi polloi' must voluntarily practice the 3 Ws (watch your distance, wear your masks, wash your hands frequently) and avoid the 3 Cs: crowded places, closed contact settings, and closed spaces.

(The views expressed are personal)

First Published:July 24, 2021, 11:17 p.m.

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