Amid Vaccine Booster Talk, Context Matters a Lot

About four weeks after Omicron (b.1.1.529) was designated as a variant of concern (VOC), evidence points to its rapid spread compared to other variants. This is most likely a result of the mutated spike protein’s ability to better bind to the receptor. This may also be because the virus is able to re-infect previously infected individuals, and infect vaccinated individuals better than other types. Preliminary data indicate a low severity of disease by Omicron. However, this has yet to be confirmed as cases accumulate and we develop a better understanding of how the virus behaves in vaccinated and unvaccinated individuals.

Laboratory studies using samples from individuals vaccinated with vaccines made on a variety of platforms, including mRNA, vectored and inactivated vaccines, have reported that neutralizing antibodies are 25-fold or more-fold less effective against Omicron than the parental strain. Another study from the United Kingdom reported that two doses of the Oxford-AstraZeneca vaccine (Covishield in India) had limited efficacy for the prevention of symptomatic infections by Omicron, but after a booster dose of an mRNA vaccine, the effectiveness was up to 71%. increases.

Even before the emergence of Omicron, more than 80 countries had introduced or planned to introduce booster doses, but Omicron’s designation as a VOC hastened the process, with countries introducing booster doses to additional age groups. Expanded or introduced boosters into the vaccination program. The most notable is South Africa. Simultaneously, vaccine manufacturers, especially those that have rapid-response platforms such as mRNA and viral-vectored vaccines, have already started targeted vaccine formulations to provide better protection against omicrons.

In India, for the past few months, there has been a demand for COVID-19 booster doses for various population sub-groups. Government appointed expert committees have been reviewing the need for boosters in India. Arguments are being made to support the introduction of booster doses in many countries – and vaccine supply exceeds demand – in India at a three-month gap between the start of COVID-19 vaccination. With the arrival of Omicron, the demand has intensified. However, does a new variant make a clear case for the introduction of the booster in India? If the scientific approach to decisions based on data is followed, the answer is not easy.

The situation is similar to the use of convalescent plasma therapy (CPT) in India. In the early months of the pandemic, CPT was recommended based on practicality, but without any scientific evidence. Later, when studies suggested that it had no or very limited role in COVID-19 management, it continued to be recommended, using anecdotal evidence from the opinion of the treating physicians or ‘expert’. There seems to be a similar push for COVID-19 boosters in India, running in newspapers and TV debates, but there is no evidence of reduced immunity from India to support this view. Often, select studies/evidence are being cited to support the argument one wants to make; 21 months into the pandemic, any decision on a booster must be based on widely scrutinized cumulative scientific evidence.

effectiveness of vaccines

On the one hand, pre-printing research papers – yet to undergo the required peer scrutiny as a standard part of the scientific process – are being used to debate the case for booster vaccination, while on the other hand, there is a recognition that Vaccines used in India are very limited on India’s data. Does the lack of evidence of reduced immunity from Indian vaccines really mean that vaccine immunity is not decreasing?

For all vaccines, antibodies rise and then fall. They may drop to undetectable levels, but if they rise at all, an immune response has been triggered. Should there be reductions in antibody levels that equal protection against disease, that would be helpful in tracking the adequacy of protection. But there is no such correlation of protection for SARS-CoV-2. The data indicate that in general, higher levels of neutralizing antibodies indicate a greater chance of protection against serious disease and infection, but there is no magic number above which there is assured protection. And this situation is further complicated by variants where antibodies may have different activity against each type.

Passive antibodies are considered functional antibodies; They are antibodies that prevent the virus from entering host cells, but there are also many other antibodies that can be found in binding assays that measure whether antibodies can stick to the virus’s cognate proteins. Levels of some of these binding antibodies parallel neutralizing antibodies, both high or both low, but again there is no cut-off that predicts anything about whether a person with high antibodies is actually safe.

A recent report on Omicron has good news about another arm of the immune system, showing that T-cell immunity was largely maintained. Expanding laboratory studies suggest that natural infection and vaccination with two doses was approximately equivalent to two doses and one booster. Most of these data are from mRNA and viral vectored vaccine combinations. We still have a lot to learn about the performance of other vaccines on Omicron and various populations and subpopulations, especially in India. It seems clear that without boosters, protection from infection is likely to be low, but how important this may be to health care systems in India, in the context of public health, is uncertain and unpredictable at the moment.

While the evidence for the benefits of boosters is emerging, we also need to worry about populations that are non-vaccinated or partially vaccinated in India and the world.

a comparison

Giving a booster dose will have different benefits for different variants. However, when globally, the supply of vaccines is dwindling, it comes at the cost of potentially huge benefits for more individuals who are still awaiting their primary two doses.

Against this background, decisions on which boosters, when and with which vaccines should be based on a public health approach, are determined by evidence and science.

Second, since each country requires vaccines and access is variable, global access to the first two shots for healthy adults needs to be prioritized. Yes, eventually boosters may be needed for everyone, but at this time, we only need to consider boosters for subgroups such as the immunocompromised (often referred to as additional doses as part of an expanded primary immunization program) ) and the people at greatest risk. In India, we should plan and execute large-scale real-world effectiveness studies in the general population, especially for vaccines that have been or will be used primarily or initially in India, so that we can provide boosters. but to develop an evidence base for the decision. general population. This should be parallel to increasing the two-dose coverage in all adults to the highest possible levels.

Third, we should not be surprised by reports of re-infection and breakthrough infection or absence of antibodies after natural infection and vaccination, especially when commercial tests are used. This is expected in both the trial design and as a vaccine for mucosal infection, as for SARS-CoV-2, rarely prevents all subsequent infections, but usually protects against severe disease for a longer period. continues.

Fourth, in the context of Omicron, India has an opportunity to plan and implement testing and tracking, which will enable the understanding of different and weakened immunity with different vaccines, if we do this. Infection and vaccination history in people affected by the type. ,

Fifth, it is an opportunity to review the performance of the vaccine program and to identify priority population groups to complete primary vaccination. It is time for the government to analyze and use integrated data from its multiple platforms for decision making.

every setting is different

India needs a road map that includes COVID-19 testing, provision of care, financial security, and advanced science communication with the general public to ensure continued adherence to COVID-19 appropriate practices, and against the disease Other safety measures can be taken to reduce further disruption. Epidemic. Discussion on boosters is necessary, but it is important that India makes its decisions, as far as possible, based on its own data. High seropositivity, as shown in the fourth round of the national sero-prevalence survey, different vaccines from the rest of the world, a different experience with the variants, all indicate that India may have an eye on the path adopted by other countries. should not be discontinued and should determine a COVID-19 booster dose policy for the general population based on local evidence and data. Context matters a lot in epidemics and epidemics.

Dr. Chandrakant Laharia is a physician with advanced training in Epidemiology, Public Health and Vaccines and is based in New Delhi. Dr. Gagandeep Kang is Professor of Microbiology at Christian Medical College, Vellore, Tamil Nadu