India contemplating role of booster vaccines

The complex question of vaccination, booster doses and Omicon variant

India contemplating role of booster vaccines

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• The story: When the protection given by a Covid vaccine course starts to wane (reduce in intensity), a booster dose can help maintain immunity levels. But for the government, vaccinating the entire population is the broader priority.
• Omicron has arrived: Right when things were coming under control, the Omicron variant arrived. India was still examining the possibility of administering booster shots of the Covid-19 vaccine, while noting that the World Health Organization (WHO) has not taken a stand on this.

1. Experts feel boosters will be required for continuing protection from Covid, while stressing that second-dose coverage is of high priority. 
2. Some suggest looking at both options simultaneously — increasing coverage and offering targeted boosters to vulnerable sections.

• What is a ‘booster’ dose: Most Covid vaccines are administered in two doses, with a few given as a single dose. A booster is an additional shot given after the protection provided by the original shot(s) has begun to decrease over time, so that people can maintain their level of immunity for longer.

1. The immunity developed by an infection or a vaccination lasts depending upon various factors, including antibodies decay over time (even memory T-cells will die after a few years or months).
2. In the past, boosters were recommended for smallpox prevention every three to five years. Tetanus toxoid boosters are also recommended today for adults and pregnant women after childhood vaccination.

• Waning immunity following Covid vaccination: In September '21, a study at ICMR–Regional Medical Research Centre, Bhubaneswar showed a significant drop in antibodies against Covid-19 within four months after complete vaccination.

1. Another study, on the immune response to mRNA vaccines, was published in Science. At six months, it found declining antibody levels, but durable memory B cell and T cell responses. Most of the B cells were able to cross-bind with the Alpha, Beta and Delta variants.
2. A study in the US showed that antibodies reduce by more than 80% six months after receiving the second dose of the Pfizer-BioNTech mRNA vaccine.

• Effect of a booster dose: BioNTech and Pfizer have said a three-shot course was able to neutralise the Omicron variant in a laboratory test; the third dose increased neutralising antibodies by a factor of 25. A study by Indian Council of Medical Research (ICMR) suggested use of booster shots of Covishield to fight emerging variants. It evaluated the neutralising potential of blood samples from people who received two doses of Covishield.
• When to administer a booster: Breakthrough infections with Delta are associated with high viral loads. If community transmission is high, boosters would help in controlling viral spread. The daily case counts in Israel remained low after booster coverage increased.

1. In India, where there are no surplus stocks of different vaccines, the policymakers need to take a call whether to aggressively enhance the vaccine coverage and whether booster shots can be given, at least to those who were vaccinated more than six months ago. (particularly those with comorbidities and frontline health workers)(b) Experts say boosters are not an answer to surges, especially in an outbreak area. In any community, mass vaccination for specific diseases provides a robust way of preventing morbidity. The goal should be vaccination of the entire eligible population with the recommended number of doses.

• Omicron: Immunity is sufficient to face normal infection. With another variant, Omicron, signals are indicating high transmissibility, so the healthcare workers will be most at risk due to increased frequency of exposure. The viral load average immunity will not be sufficient. 
• What other countries are doing: The US Centers for Disease Control and Prevention (CDC) has recommended booster shots, at least six months after their second dose, for all adults who received a Pfizer-BioNTech or Moderna vaccine. The European CDC has urged citizens to get fully vaccinated and adhere to recommendations on booster vaccination.

1. In many European countries where vaccinations started almost a year ago, there has been a surge in the pandemic. Armed with vaccine stocks, these countries and the US have rolled out booster shots for the last several months.
2. Experts say that the situation in the US and Europe is different compared to India. The number of Delta variant-caused cases is increasing in many countries.
3. There is preliminary evidence that immunity mediated by mRNA vaccines (such as those from Pfizer-BioNTech and Moderna) starts waning earlier than that mediated by adenovirus-vector-based vaccines (such as Covishield), especially for T cell response. Hence mRNA vaccine recipients might be more in need for boosters earlier than Indians (since 80+% vaccine recipients in India have received Covishield).

• WHO and boosters: According to WHO, the degree of waning of immunity and need for booster doses may differ between vaccine products, target populations, circulating SARS-CoV2 virus, in particular variants of concern, and intensity of exposure. Introducing booster doses should be evidence-driven and targeted to groups in greatest need; improving coverage of primary vaccination series should be prioritised over booster vaccination.
• India and boosters: Dr V K Paul, head of India’s Covid-19 task force, noted that “The WHO has clearly highlighted the need to complete primary vaccination first, as the most important priority. Our thinking and the overall picture are also aligned with the same approach to complete the task of vaccinating adults with two doses.” ICMR chief Dr Balram Bhargava also said India is still examining the issue of booster doses. “The data (on antibody response) has shown that vaccines are still effective after nine months to a year. This depends on the type of vaccines.”
• Summary: Experts said Omricon appears to spread very easily in the unvaccinated population, based on reports from Africa. Whether this will be the case in fully vaccinated people is unclear. Expert accounts from Africa suggest the disease itself is mild, and hospitalisation is mostly not needed. But once again, a lot more data from other places is needed before this can be confirmed as a general trend. Israel is an example of how mass booster vaccination have kept their case numbers low. Although some triple vaccinated individuals have tested positive for Omicron, they have had mild symptoms and there has been no rapid spread. 
• EXAM QUESTIONS: (1) Explain the emerging trends in vaccinating against Covid-19, and the need for booster doses in light of the Omicron variant rising. (2) What are the trade-offs that a society like India needs to make, in terms of the first universal vaccination need versus booster doses? Explain.

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