The Purpose of a Vaccine

The Hindu     3rd December 2020     Save    

Context: With three vaccines in the final stages of approval, it is crucial to define the outcomes we are expecting from population-level vaccination plans for COVID-19.

Analysis of vaccination strategy:

  • Purpose of vaccination:
  1. Individual protection: Ability to develop immunity by producing antibodies among those individuals who have taken a vaccine shot.
  2. Achieve Herd immunity: By ensuring a threshold coverage (about 60% of the population) - the proportion of the population that needs to be covered so that the entire population is protected.
  • Concerns regarding vaccination:
  1. At the individual level:
  • Vaccine efficacy: (a probability of preventing the infection) is limited by probable adverse side-effects of vaccination and the ability of the health system to deal with them.
  • Affordability: With the absence of government intervention, vaccines would be selectively available.
  1. At population- level:
  • Deciding threshold coverage: at different stages of a pandemic.
  • Accessibility: is limited by socio-economic (poor vs rich), ethical (elder or younger) and systemic (the ability of the health system to withstand after-effects) considerations.
  • Duration of protection: provided by COVID-19 vaccine.
  • Defining objectives of population-based COVID-19 vaccination drive:
  1. Prioritising Health workers and then elderly population- Will protect the health system, but maybe ineffective as patients, and their caregiver consists the largest and most vulnerable.
  2. Population-level immunity: Will help in the elimination of the pandemic.
  • e.g. New Zealand is preparing for a countrywide immunisation programme with a goal of covering the whole population with a threshold coverage.

Conclusion: Like other public health programmes, it is safe to demonstrate the success of vaccination as a public health intervention in a small population, like a block or a district, before scaling it up for the national level.