Covid vaccine: UK booster shots smack of selfishness, but failure to act could lead to increased winter infections – Professor Eleanor Riley
Do we need them? If so, who needs it and why? And, is it morally defensible to give a third vaccination in the UK, where the epidemic finally appears to be under control, while billions of people around the world are still awaiting their first dose?
The booster vaccination offers a number of advantages. It triggers a new wave of antibodies and T cells to provide protection in the short and medium term. The boosters also expand the pool of memory cells to promote very long-term immunity. They can also improve the quality of the response, by boosting the concentrations of the most effective antibodies.
Finally, if the vaccine is modified appropriately, the boosters can provide protection against new emerging strains of the virus.
So if boosters are so great, why do we actually get them so rarely?
Those of us who have cats or dogs are well aware of the requirement for annual revaccinations before we can send our furry friends to the kennel or cattery when we go on vacation.
Part of the short-term boost in immunity is for our pets’ own protection, but it’s just as much about preventing outbreaks of commercially ruining diseases in kennels. However, in humans, the only annual vaccine routinely administered is the seasonal influenza vaccine, which is offered to children, the elderly and those at risk of becoming seriously ill.
Strictly speaking, it is not a booster; although immunity to certain invariable fragments of the virus is enhanced, protection relies on the induction of entirely new immune responses against new viruses.
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We are probably more familiar with tetanus boosters: any deep or contaminated wound carries the threat of a tetanus vaccine and in some countries pregnant women are boosted so that enough antibodies cross the placenta to their unborn child to prevent tetanus associated with the umbilicus. cord infections.
Tetanus antibodies are not naturally supplemented as we rarely encounter the potent tetanus neurotoxin in our daily lives, but protection relies on the immediate neutralization of the toxin by high concentrations of the antibody infiltrating deep into damaged tissue.
Nevertheless, for most diseases, vaccination in childhood or adolescence induces a very long lasting immunity which is either sufficient on its own to protect us for life, or periodically reinforced by fleeting encounters with infectious organisms.
It is too early to say if Covid-19 is an exception to this rule. There are good arguments to adapt the current range of vaccines to reflect globally dominant viral variants and it may be prudent to use them for repeat vaccination of particularly vulnerable people.
But, so far, there is no convincing evidence that the boosters are needed simply to maintain protection in the rest of the population.
Prioritizing booster shots for healthy Britons is selfishness as only around 1% of people in low-income countries have received even a single dose and demand for vaccines exceeds always the offer.
On the other hand, by the time the need for reminders becomes evident, we could be in the throes of a winter infection wave and it may be too late to act.
To boost or not to boost is a very finely balanced appeal. Decisions are not easier.
Eleanor Riley is Professor of Infectious Disease Immunology at the University of Edinburgh