Current vaccines are good at preventing severe disease and there is increasing evidence that vaccinations help reduce the transmission of viruses. However, it does not appear to completely prevent someone from carrying it, being infected with it and transmitting it.
Current vaccines are injected therapies (e.g., intramuscular routes) and are good at eliciting systemic immunity. The types of antibodies and immune cells it triggers may travel throughout the body, defending it against invaders, but it has been reported to be inefficient at getting to the mucosal linings (protective mucous that cover the lungs, nasal area, gastrointestinal surface etc.).
This is important, because these are also places where the virus is transmitted. Thus, stopping infection in these places would mean stopping someone carrying and transmitting the virus.
Effective mucosal vaccines are also needed to trigger the production of secretory immunoglobulin A (secretory-IgA), a type of antibody unique to mucosal areas that helps fend off infections.
Unlike typical jabs, mucosal vaccines can be delivered through the nose to get vaccines directly to the nasal cavity and the respiratory tract.
Without mucosal immunity, viruses may still be lurking and infecting cells there, multiplying and, therefore, continuing to be transmitted even within vaccinated populations.
This could be what we are observing with the Delta variant, which may be driving the rise in cases around the world, even in populations with a high percentage of vaccinated individuals.
Stopping virus transmission is key, and mucosal vaccines may be the next arsenal, if not an addition to current tools.
Additionally, the design for next-generation vaccines have to address variant evasion of immunity. Updating vaccines and booster shots appear to be the current response, but it is very risky to assume that we can always update vaccines in time and win the race against the speed of transmission and rate of mutation.
Unless there is a significant increase in capacity, it will take time to produce new or updated vaccines doses, and it would face similar logistics and production hurdles.
Thus, betting on updated vaccines or boosters as the only solution in some form of future "normalcy" may be a risky choice.
One potential vaccine design strategy to increase protection against variants is to diversify the antigen target. The well-known "S" or "spike" protein is a good choice in vaccine design, given its key role in cell entry, but perhaps other targets should be included.
Virus spikes are essential to its survival and, therefore, the most prone to mutations. Expectedly, variants of concern tend to have notable mutations in the spike, resulting in structural changes of the spike which make them unrecognisable to the immune system and effectively evading antibodies that target them.
In EMIR Research's article, Covid-19 mutations call for new vaccine design, careful inoculation strategy, published in January this year, we pointed to a research where "N" proteins (in addition to "S", or spike proteins) could be a viable target.
In late May, an article in The Atlantic pointed to how an immunologist at the Massachusetts Institute of Technology shared the view that a vaccine that included both N and S targets could afford multiple layers of protection. However, the immunologist also pointed out that having too many targets may produce too many antigen proteins that shift immune resources away from sufficiently dealing with the spikes. So, balance is key.
Antigen targets could vary, but the point here is that without interventions to stop or suppress transmission (in addition to protection from serious symptoms) and widen the coverage against variants, we may lose the race against them.
There are developers exploring such vaccine technologies with similar approaches, but there appears to be just a few compared with other vaccine candidates in development, and most appear to be in early clinical trial phases.
Theoretically, next-generation vaccines with the mentioned characteristics may cover a wider range of potential variants, extending vaccine validity.
Combining this with mucosal immunity, which supresses infection and transmission, virus circulation can be inhibited and the cumulative impact will supress mutations.
Next-generation vaccines provide hope for a sustainable form of future normalcy, and a way-out of the pandemic. Current vaccines were developed at unprecedented speed, and the same level of effort is needed for next-generation vaccines.
The writer is Head of Science & Technology at EMIR Research, an independent think tank focused on strategic policy recommendations based on rigorous research.