After an 18-month saga of trials and testing, delays and divisive arguments, the vast majority of the Irish adult population are now doubly vaccinated against Covid-19. We’ve done the waiting, got the badges, and had the side-effects. But in all likelihood, these will not be the last vaccines that many of the population receive against Covid-19.
Viruses are ever-changing pathogens that evolve over time. This evolution is due to mutations. Every time a virus replicates, it had a chance of undergoing mutations in its genes. There are three outcomes for these mutations: they can be harmful to the virus, they can have no real effect on the virus, or they can have an advantageous change to the virus that might make it more transmissible or severe. Naturally, the latter are the variations that we are concerned about and which pose a threat to public health and vaccine efficacy.
There have been many variants to Covid-19 but only four “variants of concern”, as designated by the World Health Organisation (WHO), have been highlighted as particularly problematic; the alpha, beta, gamma and delta variants. Each of these variants is a different evolution of the original coronavirus that started the pandemic in early 2020. All of the variants are more transmissible than the original virus, and some cause more severe illness as well.
These variants make the vaccine landscape uncertain. The vaccines we have been immunised with were designed to fight the original Covid-19 virus. And while new variants do not completely throw away the original virus blueprint, they have changes that can make the vaccine less effective at fighting them, and something which differs across different vaccines. So what do we do in the future, if our current vaccines fail to protect us? Many scientists think the answer to this question may be booster doses.
Booster vaccines are common for many of the illnesses we vaccinate against. Immune systems’ memory isn’t perfect, and the strength of our immune response can decrease with time. For example, as infants, many people receive a vaccine against measles, mumps and rubella, followed by boosters at the beginning of primary schooling to improve their immune response to those diseases. And regularly changing the makeup of vaccines to accommodate new variants is nothing new either. Every year a different flu vaccine is developed for the different strains that are most common that year. So boosters really are nothing new.
“Many high-income countries now have 70% or more of their population fully vaccinated, and yet at the time of writing just 1.9% of populations of low-income countries have received even one dose.”
The issue with booster vaccines for Covid-19, however, is that they would further exacerbate the pre-existing vaccine inequality issue. The world is not equally well protected against Covid-19; not even close. Many high-income countries now have 70% or more of their population fully vaccinated, and yet at the time of writing just 1.9% of populations of low-income countries have received even one dose, according to Our World in Data. To even be considering booster shots in Ireland shows that we are in an incredibly privileged position. With all this in mind, in early August the WHO called for a moratorium on any countries giving boosters until the end of September at the earliest, to prioritise getting vaccine supplies to the regions that are still critically under-vaccinated.
There is a strong case for ensuring limited supply goes to low-income countries, and not as boosters in high-income countries. Many experts believe that these vaccines should be distributed in a triage-like manner: deal with those at most severe risk first, which is of course those who remain unvaccinated.
Doing this also has direct benefits for the high-income regions also: it could slow down the emergence of new variants. Viruses need to be transmitted from person to person for effective mutations to spread and become variants of concern. Once more of the world has been vaccinated there is less chance for variants of the virus to arise. Naturally, we want as few variants of the virus as possible, due to the risk they post to vaccine efficacy and transmissibility. Professor Jonathan Gruber, of the Massachusetts Institute of Technology, estimated that a first vaccine dose in less-vaccinated countries like India could be eight times more impactful than a booster shot in the United States.
The jury is also still out on whether boosters would actually deliver a significant increase in protection to those that are not at high risk from Covid-19, or how much our vaccine protection wanes. Scientists can clearly observe a reduction of antibody titres as time passes post-vaccination, as with all vaccines, but it is hard to conclusively say that this is really reducing the protection we experience.
“The feeling of being protected can invite much less careful behaviour than people do pre-vaccination.”
For instance, while we are now observing increased levels of hospitalisations of the elderly than we did immediately after the vaccination of this grouping, this might not be due to waning protection. This could in fact be due to societal factors and the general relaxation of protective measures such as masks and social distancing among this age group once they were vaccinated. The feeling of being protected can invite much less careful behaviour than people do pre-vaccination.
There’s also a question of what we want from the vaccines and what it is reasonable to expect them to do. If the metric is that we want immunisation to prevent deaths and hospitalisations, then booster shots really will not be required for most of the world’s population for some time.
One possible approach is to only provide booster shots to the immunocompromised, in order to have as minimal an impact on global vaccine supplies as possible. We must be careful to keep the vaccines we use in richer countries to a real minimum, and truly to just provide boosters to those in dire need of them. Otherwise we enter the territory of so-called vaccine nationalism, which will not help anyone in the long run. Hoarding vaccines and protecting those who are much less likely to be hospitalised or to die from the virus — while the pandemic rages on, taking countless lives in less economically developed regions — can never be morally justified.