Evaluation criteria for a vaccine
- Evaluation of candidate vaccines for COVID-19 should be done on technical parameters and programmatic suitability.
- An ideal vaccine would provide all of these
- Immunity that is of a high degree (90% + protective especially against severe illness), broad scale (against different variants) and durable (at least five years if not lifelong);
- A vaccine that is safe (little or no side-effects and definitely no serious adverse effects);
- A vaccine that is cheap (similar to current childhood vaccines);
- A vaccine that is programmatically suitable (single dose, can be kept at room temperature or at worst needs simple refrigeration between 2°C and 4°C, needle-free delivery, and
- A vaccine that is available in multidose vials, has long shelf life and is amenable to rapid production.
A difficult vaccine to develop
- Historically, we have faced difficulties in the development of coronavirus vaccines.
- Although there were some attempts at development of vaccines against Severe Acute Respiratory Syndrome (SARS) and the Middle East Respiratory Syndrome (MERS), there are no licensed vaccines for any coronavirus yet.
Possibility of re-infection
- Previous coronavirus vaccines were found to be immunogenic (generate antibodies as in phase II) but did not effectively prevent acquisition of disease (phase III) fuelling a concern that vaccination may not induce long-lived immunity, and re-infection may be possible.
Inadequate long term experience
- There are also safety concerns due to immunological consequences of the vaccine as these vaccines use newer techniques with which we do not have long term or large population experience.
Need for post-licensure surveillance system
- About the safety of vaccines, there are always possibilities of rare (one in million) or delayed (by months or years) serious adverse events which will come to light only after mass vaccination has started which requires a good post-licensure surveillance system to be in place.
What should the government strategy be while choosing a vaccine and for vaccination?
Ranking by risk category
- The first rule would be to not to put all the vaccines in one basket as we know that the government has planned for vaccine supply from different sources.
- The World Health Organization has issued guidelines for prioritisation for vaccine recipients. For this, we need to rank population sub-groups by risk category (risk of infection or adverse outcome or economic impact), and by programmatic ease of vaccination — based on their captivity (health-care workers, organised sector, workplace, schools), and access to existing channels of vaccination (pregnant women and children).
- Start with where these two criteria intersect — health-care workers followed by policemen.
Use multiple channels
- The third rule is to use multiple channels to immunise the population. Other important considerations would be of equity and cost.
Vaccinating general population
- Problems will arise as we move towards vaccinating the general population from frontline workers, even high-risk groups (the elderly and those with co-morbidity) in the general population.
- It might be easier to vaccinate the institutionalised elderly as compared to community-dwelling ones.
- Solution: The only orderly option is to create some sort of a technological solution of a queuing system based on an earlier registration process for age and presence of co-morbidity and allotment of appointment in a nearest booth.
- The greatest challenge would be to immunise the poorest and the most vulnerable(slums/migrants/refugees/people with disabilities) because of access issues.
- This must be by an outreach or camp approach (booths along with web-enabled appointments facilitated wby civil society); a programmatically suitable vaccine will have to be prioritised for them.
- Since it is expected that the pandemic would start receding once we protect about 60% of the population (in terms of coverage x effectiveness), the possibility of using a ring immunisation strategy (immunising the population around reported cases), even earlier arises.
Dealing with ‘pay and get’
- One major challenge would be that many people would be willing to pay for the vaccine and ask for expedited access.
- The government can allow the vaccine to be available in the private sector at a market-driven price for such people however it will be ethical as well as cost-saving for the government, if it does not divert vaccines from the government-driven programme.
- Many countries have already published their prioritisation policy whereas in India the details are not available in the public domain.
- It is critical that the government has a fair, transparent and published policy in this regard even if it results in heartburn in some quarters.