Booster dose of COVID-19 vaccine: To give or not to give?

Shobha Shukla / Bobby Ramakant *

With almost 19 million new COVID-19 cases reported, the third week of January 2022 recorded the highest-ever weekly number of new infections so far in the pandemic’s history. This was an increase of 20% more cases than the earlier 'highest-ever record' which was set in the previous week.

With over two years into the pandemic, we cannot miss the writing on the wall: we are failing to break the chain of infection transmission. And to add insult to injury, we have failed to roll out over 9 billion vaccine doses equitably in the world.

'Fully unvaccinated' are the hardest hit now

Currently, up to 90% of the COVID-19 positive people who are hospitalized, are unvaccinated. It appears that those who are left ‘fully unvaccinated’ are the ones most at risk of developing serious outcomes of COVID-19 if they get infected, while the privileged people who are fully vaccinated get booster after booster.

“How can we miss the obnoxious levels of inequalities, not just between rich and poor nations, but also within the rich ones: most of the people who are hospitalized due to COVID-19 currently even in rich nations, are those who are unvaccinated” rightly said Dr Ishwar Gilada, noted infectious disease expert who was speaking with CNS (Citizen News Service).

While on one hand we have to do all-what-we-can to break the chain of infection transmission, on the other hand it is equally important to ensure that people with co-morbidities and other identified groups at higher risk of serious outcomes of COVID-19 are fully vaccinated worldwide. One big price we are paying as global humanity for failing to vaccinate equitably is the emergence of new corona virus variants that are posing heightened challenges.

If we look at the World Health Organization (WHO) goal to fully vaccinate at least 70% of the population in every country worldwide by June 2022, then not surprisingly, the progress is sketchy - 109 out of 193 countries will fail to meet this target. More alarmingly, 36 countries have not been able to vaccinate even 10% of their population.

Despite knowing it is more important to ensure that unvaccinated people get their primary vaccine shots on high priority, rich and poor nations alike are going ahead with providing booster doses to the fully vaccinated people. Some countries like Israel and Germany are giving out the fourth dose (second booster). Even a call given by the WHO for a global moratorium on boosters till December 2021, did not deter the rich nations from going ahead with the third shot of vaccines.

One in four vaccine shots used as a booster

Currently, one in every four vaccine-doses is being administered as a booster dose in one of the 126 countries that have included booster-recommendation in their national guidelines for management of the pandemic. In many of these countries, which are administering booster doses, the coverage rates for complete primary vaccination are below 30%.

So should we keep providing booster after booster to those already vaccinated, rather than reaching out to the unvaccinated too? Or do we have to do both with equity and science as the guiding stars?

According to the WHO, booster doses are administered to a fully vaccinated person if, with time, the immunity and clinical protection has fallen below a rate deemed sufficient in that population. The objective of a booster dose is to restore vaccine effectiveness from that deemed no longer sufficient.

WHO Strategic Advisory Group of Experts (SAGE) on Immunization had met on 19 January 2022 and looked at the scientific evidence regarding boosters. There is emerging, yet limited, evidence of how boosters help increase vaccine efficacy against both variants (Delta and Omicron) of the SARS-CoV-2 virus. There is no booster data on long-term duration of protection in terms of hospitalization, severe disease, or death.

Scientific studies on Omicron variant are very few and with limited follow up. More data will be needed to understand the potential impact of booster vaccination doses on the duration of protection against not only severe, but also mild disease, infection, and transmission, particularly in the context of emerging variants.

Dr Soumya Swaminathan, WHO Chief Scientist and former Director General of the Indian Council of Medical Research, lists three aspects that can affect immunity:

- The older a person is, more underlying conditions might be there; or if the person is on immunosuppressive drugs, the immune system may be weak, and so may need additional help to boost that immune response.

- Different variants of the corona virus have different levels of immune escape, and with Omicron we know that it has the highest levels of immune escape or immune evasion so far.

- There are differences between the different vaccines in how high the antibody response is, how long the protective immunity lasts and other characteristics.

Dr Swaminathan says that "at this point in time, our focus, considering that we still have so many unvaccinated people in the world, is to provide primary doses to those who have not been vaccinated so far, while at the same time trying to protect the most vulnerable in every country's population.”

Dr Mike Ryan, WHO Executive Director for Health Emergencies Programme, said that having a third dose of vaccine may raise one’s antibody levels but long-term benefits may not be the increase one gets in antibodies. “It may be that that third dose is allowing your immune system to mature,” said Dr Ryan.

Let us remember that a vast majority of people who are still being hospitalised due to COVID-19 are those who are unvaccinated. In most cases of breakthroughs occurring in vaccinated persons, outcomes are less severe than those in unvaccinated persons. “However, emerging data consistently show a decline in vaccine effectiveness against COVID-19 with time since vaccination, and more significant decline in older adults. This evidence is mostly based on observational studies that may be subject to confounding factors" reads WHO SAGE document of last month.

While vaccine supply is growing, it is not yet at optimal level, and it is not evenly distributed. Lower income countries have had far less access and face unpredictable and irregular supplies. WHO SAGE meeting of last month noted that it is only by late 2022 that supply of vaccines will be sufficient for extensive use as boosters in all adults, and beyond, should they be broadly needed.

Introducing booster doses should be firmly evidence-driven and targeted to the population groups at highest risk of serious disease and to the healthcare personnel.

Safe and effective vaccines are a game-changing tool. But let us not forget that vaccines alone will not stop the acute stage of the pandemic. In the foreseeable future we must continue to wear masks, frequently sanitise our hands, ensure good ventilation indoors, physical distancing and avoid crowds.

Booster after booster given to fully vaccinated people, while many remain 'fully unvaccinated' will not help either. Vaccines need to be administered to the most at risk people on higher priority and then to all eligible people worldwide. Ending the acute stage of the pandemic is possible and so is breaking the chain of infection transmission.

But to achieve this, our leaders will have to use their political acumen to replace populist measures with those backed by science and evidence and rooted in equity.