Tackling emerging SARS-CoV-2 variants

By Susha Cheriyedath, M.Sc.Jun 29 2021

An international team of authors has published a special report in The New England Journal of Medicine titled 'SARS-CoV-2 Variants and Vaccines’, which presents global strategies for the possible escape from vaccine-elicited immunity.

NEJM Special Report: SARS-CoV-2 Variants and Vaccines. Image Credit: NIAID

There is a possibility that dangerous viral variants could appear with resistance to the current vaccines intended to prevent coronavirus disease 2019 (COVID-19). Also, if some variants are more transmissible or virulent, we will see an even greater need for effective public health measures and vaccination programs. It is therefore imperative that the global response is timely and science-based.

Tracking the emergence of new severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) variants of concern (VoC) is the first and foremost priority.

As part of the global response to VoCs, scientific approaches should be employed to assess whether the currently available vaccines are losing their effectiveness and to develop new, improved vaccines that are more effective against existing and future variants that might continue to emerge.

A global approach to research and vaccine development via the World Health Organization (WHO) is also a priority.

Evaluating currently available vaccines for efficacy against SARS-CoV-2 variants of concern

It is vital to collect the clinical data after deploying existing vaccines to determine if these vaccines are losing effectiveness because of new variants. Carefully planned observational studies and randomized trials of one vaccine vs. another, vaccines vs. placebo, or different vaccination regimens with different dosing, number of doses, and dose intervals are essential in achieving this.

In areas with limited vaccine supply or distribution capacity, vaccinating randomly selected target populations could provide insight into the vaccine's efficacy against major SARS-CoV-2 variants.

Random vaccine assignment is a concept that can be built into public health programs, and eligible individuals could be randomly assigned appointments to receive vaccines with a shorter or longer interval between vaccine shots or with different vaccines.

This strategy may allow adequate randomization without affecting the vaccination program and disturbing vaccination capacity and also offer critical insights into vaccine efficacy against various strains of the virus.

Evaluating the effect of new or modified vaccines against variants of concern

The need of the hour is to plan the development of vaccines modified to protect against SARS-CoV-2 variants resistant to available vaccines.

Studies of modified vaccines with a new antigen that has proven efficacy against previous viral variants should assess the ability of these new vaccines to induce immune responses in individuals who have not had a SARS-CoV-2 immune response and in previously vaccinated persons.

Evaluating neutralizing responses against many variants of concern and against the prototype virus may help determine if multiple vaccines (or a polyvalent vaccine) are needed.

New single-dose vaccines that are more effective than previous vaccines against SARS-CoV-2 variants and noninjectable ones and avoid cold-chain constraints are ideal solutions to problems facing global vaccination efforts.

These new vaccines' development and deployment strategies should consider the possibility that multiple variants may be present in the same area. Studies on different prime and booster vaccines would be valuable in this scenario.

Partially effective interventions encourage SARS-CoV-2 evolution

Variants of concern resistant to natural or vaccine-induced immunity will overtake previously circulating strains only if their immune escape capability leads to increased viral fitness.

Prolonged viral replication in immunocompromised persons, individuals with partial immunity, or situations that promote rapid transmission of the virus (crowded living conditions) could be significant drivers for the emergence of variants with immune escape capabilities.

Antibody-based treatments in scenarios of limited or untested efficacy might also contribute to the emergence of variants of concern that are resistant to natural and vaccine-induced immunity.

The larger the number of infected individuals, the greater the emergence of new variants of concern. Thus, social distancing, mask usage, and the targeted use of vaccines to reduce infection and transmission can be extremely helpful in limiting the evolution of the virus.

Coordinating global response to SARS-CoV-2 variants of concern

Since new variants of concern may emerge anywhere globally and spread to other parts quickly and the modification of vaccines can have international repercussions, vaccine development, modification, and deployment should be considered global enterprises coordinated by the WHO. Assessing the need for modified vaccines, evaluating the new vaccines, and facilitating scientific understanding of the risk posed by new variants are all efforts that require global coordination.

Open scientific discussion is essential to identify which variants of concern deserve the attention of the scientific community. In addition, a global framework is needed for effective decision-making about the type of antigens to be included in SARS-CoV-2 vaccines and maintaining confidence in the processes used to develop, test, and deploy these vaccines.