The immunity quest

After claiming more than 54 lakh lives worldwide, and affecting almost every single human on the Earth, the pandemic is showing no signs of receding. The new variant — Omicron — is an assertion of the fact that Coronavirus is here to stay, among us, killing us daily in large numbers, and crippling our lives beyond count.

The best armor that humans have in their kitty — double dose vaccination — is failing to curb the transmissibility of the virus. The double dose we had been desperately longing for over two years has been turned ineffective — through what? A simple modification of spike proteins in the virus!

But are humans losing the war? No, humans may die, they may suffer, but they never lose. The fight is on, and the answer, for at least the time being, is the booster dose. The whole human race, which was until a few months back running behind the goal of primary vaccination, is now running pillar to post to achieve the shifted goalpost — almost in a blinded fashion.

But this perceived panacea of boosters has its own set of limitations. In the first place, it is not for all. Only well-off countries are able to afford booster doses for their population while many nations are still struggling to achieve primary vaccination. Vaccine inequity is now out with its naked ramifications that experts had been warning since long. Further, the efficacy of booster doses in containing the spread of the Omicron variant is limited on several counts.

In this article, we shall look at the prospect of booster doses in India. More importantly, it would be pertinent to retrospect on balancing the need for booster in well-off countries with primary vaccination in low-income countries. But first, we shall start with the basic concept of immunization.

Immunisation mechanism

Immunity against a particular pathogen refers to the ability of the body to fight against that pathogen. Our body acquires immunity after being exposed to the pathogen and fighting against it for some time. In case of Covid-19, a person acquires immunity either after being recovered from Covid-19 or through controlled implanting of the modified prototype of the virus — enabled through vaccination.

White Blood Cells — also called immune cells — fight against infections in our body, including Covid-19 infection. WBCs are of different kinds and have different defense functions. One of the WBCs — Macrophages — helps the body by eating up the pathogen and leaving behind antigens; this makes it easy for the body to identify these antigens and produce antibodies to fight against them. The production of antibodies in the body is carried out by B-lymphocytes (or B-Cells). Most of the vaccines are currently designed to focus on creation of antibodies through B-Cells. The plus point of B-Cell response is that it counters the virus components before the human body is infected. This is analogous to entry-level gatekeeping for the virus. On the flip side, the body's capacity to produce antibodies is limited against the rapidly multiplying viruses.

This is where the second defense mechanism sets in. The T-lymphocytes WBCs (or T-Cells) play a rather attacking role. A certain component of T-Cell — CD8+ T-cell — kills the virus in the infected parts of the body. Certainly, both the B-Cell and T-Cell responses are of critical importance to combat the virus. The three major types of vaccines — mRNA vaccines, protein subunit vaccines and vector vaccines — carry out the same function of facilitating the creation of T-Cells and B-Cells.

Body's defense system memorizes its response to act against similar onslaughts from the virus in future. There is lack of conclusive evidence yet as to how long is this memory retained in the case of Covid-19 infection. The losing memory of the defensive WBCs may lead to waning of immunity in the fully vaccinated persons over time — thus creating a need for booster doses.

Universal vaccination vs booster doses

One thing is for sure, booster doses of Moderna and Pfizer — both mRNA vaccines — are known to reduce the risk of Omicron significantly. Whether it is true for other sets of vaccines is not yet clear. The reason is there isn't enough data to either substantiate or negate the point.

Presently, 150 countries across the world are receiving the Pfizer BioNTech vaccine. This includes almost the whole of Americas, Australia, Western Europe and some countries in Africa along with limited countries from Asia. Moderna, on the other hand, is administered in 83 countries, including most of the countries in Northern America, Western Europe and Australia. Oxford AstraZeneca, being administered in 183 countries, remains the most popular vaccine. It is being administered in India as Covishield.

At least for the countries that are administering Moderna and Pfizer, it can be said that booster doses could lead to containing the spread of Omicron at regional level — country level at best. But how far will it be successful in rooting out the global pandemic is questionable — as concentration of booster doses in richer parts of the world will leave poor pockets behind to become virus dumping grounds.

The World Health Organization (WHO) has decried the indiscriminate rush towards the booster dose vaccination by European nations and the USA. WHO's stated concern is that the world has only enough vaccines to give double-dose vaccines to the global population and boosters to at-risk immunocompromised individuals. Only then, the world will move towards eliminating the pandemic. The UN, World Bank, IMF and WHO had called for commitment in August to administer at least one dose to 40 per cent of the population of each country in the world by the end of the year. While many developing countries just managed to cross the mark, almost all the nations in Africa — barring just a few — failed to do so.

Contrary to this, Raka Banerjee, Project Coordinator in the Development Data Group at the World Bank, in an interview on July 28, stated that 84 per cent of the vaccines went to high and upper middle-income countries. Countries like the USA and the UK have found it more suitable to use the heavy stockpile of the vaccines to boost their entire population. In doing so, there is no doubt that these countries are ensuring foolproof safety of their citizens. But this will leave some pockets in the world where the virus could easily mutate and then spread to the entire world again.

But is it appropriate to demand that Western countries compromise with the safety of their citizens? In order to answer this question, we will have to understand the difference between double dose of vaccination and booster dose.

Booster dose over double dose

Two types of protection can be expected from the vaccines — one, that it would prevent severe illnesses and hospitalization; and two, it will put a check on transmission of the virus. Primary research and experience have shown that the double dose of the vaccine potentially protects people from severe illnesses, provided that they are not at-risk or immunocompromised. The two doses of vaccination, however, are known to fail in preventing the transmission of the virus. This effectively means that most of the double-vaccinated people will not die from Omicron but they may likely catch the infection.

The booster dose, on the other hand, will prevent people from both severe illnesses and transmission. The need for boosters is also emphasized on account of waning immunity. This argument lacks conclusive evidence as no specific timespan for waning immunity of various vaccines is ascertained yet.

India's prospect for boosters

Until a week back, India had four vaccines in its kitty — Serum Institute of India's Covishield, Bharat Biotech's Covaxin, Russian vaccine Sputnik V and Zydus Cadila's ZyKoV-D. Covishield and Sputnik are adenoviral vector vaccines while Covaxin is an inactivated-whole virus. Evidence suggests that the type of booster dose should ideally differ from the first two doses if the primary vaccine happens to be an inactivated-whole vaccine or adenoviral vector vaccine. In India, 90 per cent of the vaccination has been carried out through Covishield.

DCGI's approval of two new vaccines — Hyderabad-based Biological E's Corbevax and Serum Institute of India's Covovax — is relevant in this context. Both the vaccines differ from Covishield, Covaxin and Sputnik in their composition. Corbevax and Covovax are protein-based vaccines and could potentially be considered for booster dose.

The real breakthrough, however, would be the two vaccines that are in the pipeline — Bharat Biotech's Intranasal vaccine and Pune-based Gennova Biopharmaceuticals Ltd. Gennova vaccine is of prime interest as it is known to be India's first mRNA vaccine. Experts across the globe have suggested that mRNA vaccines are the best candidates for booster doses.

But then again, efficacy of all these vaccines is more speculation and less evidence-based proof. Further, given the long gap prescribed between the second and the third dose suggests that booster in India is still a long shot.

Immunisation across the world

When it comes to administration of booster doses, nearly half of the world is yet to make a foray into what could safely be called a privilege of high-income countries or regions.

Continent-wise, almost the whole of the Americas minus a few countries — Mexico, Venezuela, Nicaragua, Suriname and French Guiana — have made a tryst with booster dose. While the South American nations, Chile and Uruguay, top the chart with 55 per cent and 44 per cent boosted population respectively, the USA and Canada, being larger nations, have boosted 20 per cent and 17 per cent of their populations respectively. Brazil, in South America, has administered booster doses to 12 per cent of its population. Nearly 68 per cent of the population in Brazil is fully vaccinated while 79 per cent is partially vaccinated. Other nations crossing the double-digit mark in terms of booster dose include Argentina (11 per cent) and smaller countries like Cuba (12 per cent) and Dominican Republic (13 per cent).

The most heavily boosted region in the world — though a relatively smaller one — is the Western Europe. To have a glimpse into the region, the percentage of population having received a booster in countries is: Iceland (55 per cent); the United Kingdom (49 per cent); France (31 per cent); Ireland (41 per cent); Germany (36 per cent); Austria (41 per cent) Hungary (32 per cent); Greece (31 per cent); Serbia (25 per cent); Italy (28 per cent); Slovenia (22 per cent) etc. Only a few small countries in the region like Croatia, Ukraine, Romania, Estonia etc. have not administered booster doses to its population.

To paint the picture in stark colours, we now discuss the second-largest and second-most populous continent in the world — Africa. Africa hardly leaves any scope to discuss boosters, as only two countries in the northern part of the continent — Algeria (0.1 per cent) and Tunisia (7 per cent) — have received a booster dose. In Africa, one can see the naked reality, and one will be forced to talk of the real things at hand — the bid to vaccinate, and not boost.

Sadly, for many of the countries in the continent, the proportion of vaccinated (partially or fully) continues to linger below the double-digit mark — Nigeria (2.2 per cent), Sudan (2.9 per cent) South Sudan (1.6 per cent), Mali (2 per cent), Ghana (7.7 per cent); Zambia (6.1 per cent), Ethiopia (1.4 per cent); Madagascar (2 per cent) — and the list doesn't end here.

Brace up for more shock, as there are a few countries in Africa for which the percentage of fully vaccinated population is in points, for example, Democratic Republic of Congo (0.1 per cent) and Chad (0.5 per cent). And then the world talks of booster vaccines. A question that should intrigue every human is: How far can we afford to take top-up vaccines year after year, because unless the entire world is shielded from the virus, no one is safe and variants will keep coming from the pockets we have created for ourselves. This is the time the world should realise it is digging its own grave by neglecting the needs of poorer nations.

For Asia, the booster scenario has been a mixed one. Around half of the continent (area-wise) is left untouched from boosters. Among the top boosted countries of the continent include South Korea (32 per cent) and Mongolia (28 per cent). Among the bigger countries, China has administered booster doses to 8.5 per cent of the population and Russia has administered boosters to 4.8 per cent of its population. The untouched countries in the continent include Afghanistan, Pakistan, Nepal, Bangladesh, Myanmar, Uzbekistan, Turkmenistan, Kazakhstan, Tajikistan, Kyrgyzstan, North Korea and India. Among these countries, Afghanistan and Kyrgyzstan are the lowest faring countries, with the fully vaccinated percentage in Afghanistan being lower than 10 per cent. It must be noted that Sri Lanka, being a smaller nation, has boosted 16 per cent of its population and fully vaccinated 63 per cent. Fully vaccinated figure in China is 86 per cent, Russia 46 per cent and India 43 per cent.

In the southern part of the world, the Australian continent has an impressive vaccination statistic, with 8.5 per cent boosted, 78 per cent fully vaccinated and 80 per cent partially vaccinated. The Middle East is also faring well with a caveat of sharp inequality in a compressed region.

Conclusion

It is clearly a matter of reflection, how much priority is to be given to the boosters and how much to primary vaccination, knowing that primary vaccination is critically important to prevent severe illnesses and death, as also to prevent the new variants from propping up.

Views expressed are personal