Episode #27 - Vaccines, variants & herd immunity

26 February 2021 | Science conversation

Gabby Stern:

Welcome to Science in 5, WHO's conversations on science. I'm Gabby Stern. We're continuing our conversation about vaccines. WHO's Chief Scientist, Dr. Soumya Swaminathan, is here to talk to us about variants and how vaccines work with them. Welcome, Soumya.

Dr. Soumya Swaminathan:

Hello, Gabby.

Gabby Stern:

So our first question is as follows: as new variants emerge and as we learn more about how much protection the current batch of vaccines provides against them, people are wondering if they should wait until a more efficacious vaccine is available or should they go ahead and get vaccinated now?

Dr. Soumya Swaminathan:

The good thing is there's lots of vaccines in development. But currently there are only a few that have completed clinical trials and that have had regulatory approval for use in countries. The good thing about all of these vaccines which have been approved, is that they offer a lot of protection against severe disease, hospitalisation and death. And that's what we want. We want to reduce deaths. We want to prevent people from getting sick and going into hospital. We're still learning how effectively these vaccines protect against mild disease or asymptomatic infection. With the variants that are being described from different countries, people are asking these questions because there's some data coming showing that vaccines may be less effective in preventing against some of these variants. However, even in those countries, all of the vaccines that are approved still are very likely to protect against severe disease and hospitalisation and death. So what's really important now is for people in countries who have been prioritised, who are in those risk groups, the health workers, frontline workers, the elderly and others who have been prioritised, must get their vaccines, because what we want is to prevent people from getting really ill or dying from COVID-19. 

Gabby Stern:

My second question is, what can we expect from the research and development pipeline for vaccines? What would future vaccines look like? 

Dr. Soumya Swaminathan:

What's really amazing here is the amount of scientific and technological innovation that's happened in the short period of time. So while we have a few vaccines now that have been approved for use, what we are looking forward to is the next generation of vaccines that will be single dose, that can be stored at room temperature, that's safe for use in pregnant women, that can be taken either through a nasal spray or even orally and will provide long lasting immunity. So, there's all of these vaccines in development. With the news about the variants and the fact that some mutations in these variants seem to prevent the antibody binding to the virus as compared to the wild-type virus, what's also happening now is that vaccine manufacturers and developers are working on the next generation of vaccines using the same platform, but incorporating the new antigen, the new protein, which has the mutations of interest that have been incorporated so that the antibodies are now developed to this new form of the spike protein. WHO is working with regulators around the world, first of all, to try and determine when a vaccine change will be needed, and secondly, what clinical and immunological data the developers will need to provide in order for vaccines to be certified for wide use.

Gabby Stern:

In some cities, serological studies have revealed that about half of the population has antibodies. Does this mean that these places, these cities are approaching herd immunity? And should people relax the precautions in these places?

Dr. Soumya Swaminathan:

So WHO has been keeping track of these seroepidemiological studies and at last count there were almost 500. And if you take them altogether, less than 10 percent of the world's population actually has antibodies to this virus. Of course, in some settings, like particularly in the very high density urban settlements, there are pockets where 50, 60 percent of the population has been exposed to the virus and has antibodies. But that doesn't mean that the whole city or the whole province or the state or the country is now achieving herd immunity. The same individuals who are living in that community, the moment they go outside to a place where there is less herd immunity and if they don't have antibodies, they will then become susceptible. The only way of achieving herd immunity at that scale is through vaccination. And that's what we're focusing on now through COVAX to get vaccines out to all countries, to vaccinate populations as soon as possible. Till that happens, we need to continue to take all the precautions that we've been advised to and that we've been doing for all these months. And this is, along with the government, taking all the actions that they have been taking in order to keep transmission down as low as possible.

Gabby Stern: