With the Omicron COVID-19 variant disturbing the normal living in countries across the world, governments are introducing various safety measures to contain the spread of the virus. A number of countries are rolling out COVID-19 vaccine booster drives to enhance the protection against the variant.

For instance, Israel has rolled out a fourth COVID-19 vaccine dose for some citizens. As per reports, the country has administered the third vaccine dose to more than four in 10 of its population. Noting the concerns related the Omicron variant, Israeli health experts recommended fourth dose for those above the age of 60 years and healthcare staff.

Importance of booster dose:

Boosters provide the necessary strength to the body and enhance immune response against COVID-19 after the effects of a previous dose start to fade. Furthermore, it increases the number of neutralizing antibodies - the immune cells that combat the virus.

It is significantly helpful in fighting Omicron as the new variant contains dozens of mutations and is better able to evade protection from vaccines. Hence, a stronger immune response is needed to fend off the Omicron variant. Boosters are already being administered to eligible people in various countries, except sub-Saharan Africa.

Currently, Chile is leading in terms of higher booster administration with 53 percent of its population having received the booster dose. Other nations such as Iceland (52 percent), Israel (46 percent), Uruguay (43 percent), the UK (43 percent), Denmark (35 percent), Malta (34 percent), and the UAE (33 percent) are also demonstrating proactive measures in providing the booster vaccination.

Earlier this month, Pfizer's chief executive Albert Bourla stated that a significant number of nations can require fourth doses for strengthening protection against emerging variants.

While Israel is forging ahead with the initiative countries like the UK are offering a fourth dose of COVID-19 vaccine to highly-vulnerable categories.

Will boosters be needed indefinitely?

According to Dr Andrew Freedman, infectious diseases specialist at Cardiff University in the UK, immunity against Coronaviruses tends to wane over time and boosters are helpful in increasing antibody levels.

Moreover, even if the antibody levels decline, the individual may have immunity as the immune system contains a “memory” developed by vaccination or previous infection. It can be mediated by memory B cells (white blood cells that help in rapid production of antibodies against a particular antigen such as SARS-CoV-2).

At the same time, memory T cells are also important as they remain in the blood for long periods after vaccination or infection. It can foster a rapid response against the same antigen.

Dr Bharat Pankhania, a senior clinical lecturer at the University of Exeter in the UK and consultant in communicable disease control, underlined that in certain infections, such as Hepatitis B, individuals may require five or six vaccine doses before gaining long-term protection.

“With respect to Coronavirus, we don’t know whether they will need four or five, or a reformulated vaccine. However, we may need quite a few before we [achieve] sustained immunity, if we do," he added.

How will virus evolution affect the need for boosters?

The prevalence of the COVID-19 virus will determine the long-term need for boosters. With the Omicron variant, scientists are detecting early signs that the virus is becoming less harmful to infected individuals. However, infectiousness has increased.

In this regard, Dr Freedman added that if the impact of Sars-CoV-2 virus reduces, boosters may not be required in long run. As of now, there are four coronaviruses that cause colds.

“If it remains a serious virus with serious hospitalisation and death risk, an annual booster will be needed,” he added.

Furthermore, new variants are likely to evade the protection of existing vaccines. Therefore, there is an increased need for booster doses to strengthen immunity against the virus. As a result, vaccine developers are reformulating vaccines to offer them as boosters in the future.

Dr Pankhania pointed out that new vaccines may be needed to cope with new variants. Experts have also called on world governments to increase vaccine supply to Africa and other regions to help them in protection against new variants.

In addition, the next-generation vaccines may also change the need for boosters in the future. Prof David Taylor, emeritus professor of pharmaceutical and public health policy at University College London, later vaccines may offer more durable immunity against Coronaviruses.

“What we don’t know is the extent to which people who’ve been exposed from childhood will have a better long-term response than people exposed only in adulthood. But we’re looking decades down the line. Probably we’ll need boosters [for the moment], but maybe the intervention of second and third-generation vaccines will mean that’s no longer necessary,” added Prof David Taylor.