the importance of booster dose to plan ahead

Relevance: To understand the latest developments in the vaccination process.

Synopsis: The COVID crisis, unlike other health issues is new and has devastated the world economies.  Recovery from Covid-19 is dependent on faster adoption of the best vaccination process.

Introduction:

1. WHO launched an expanded immunization program in 1974, the experience gained through this has greatly helped in vaccine production and rollouts.
2. Vaccines may be classified as:
   • Live infectious vaccines
   • Non-replicating non-infectious vaccines
3. The first one contains a live but attenuated virus. They replicate in the body without producing the actual disease. The final effective dose may contain billions and trillions of Viruses. So immune responses to replicating live virus vaccines – both antibody and T-cell immunity – are robust and lost lasting.
4. Non-replicating vaccines include commonly known vaccines like DPT, Hepatitis B. In this, a tiny amount of antigen is injected. It may also include stabilizers, preservatives, and adjuvants.

What is the need for a booster dose?

In order to get long-lasting immunity with non-replicating vaccines, we need multiple doses.

Priming doses:

Initial doses are given in quick succession. The immune system responds well, but is accompanied by low levels of antibody and T-cell immunity. However, over a period of time, the antibody levels wane away in all individuals. Hence, we need subsequent doses.

Booster doses:

There are doses that are administered after ‘priming doses’. Even non-replicating vaccines require priming and boosting. E.g. Tetanus vaccine is given once every 5 to 10 years. The experience shows that booster dose scheduled after 6 to 12 months after priming dose produces a long-term response.

All current Covid-19 vaccines fall in the non-replicating category and hence require booster doses.

The current schedules

• The current doses of all vaccines – J&J, Pfizer, – are only priming doses. After 6 months to 1 year, booster doses will be needed.
• This becomes more important for the elderly, people who have undergone an organ transplant, or have other co-morbidities.

The strategy ahead

1. Given the fact that the virus is mutating and becoming deadlier, the pandemic is here to stay. Thus, approvals have been sought by companies like Pfizer for booster doses.
2. India faces an ethical dilemma – though booster doses are necessary, this cannot be started till everyone receives priming doses.
3. India could plan to give priming dose to everyone and give third or booster dose to special category people. This can then be followed by a booster dose for the rest of the population.