• The sooner we start using booster jabs, the more likely it is that we will need them.
• In the eight months since Covid-19 vaccines first became available, nearly four billion doses have been administered, and yet the number of cases and deaths continues to rise.
• Why? For the simple reason that we are not making the most efficient global use of the doses available. Now, as evidence is emerging about the potential benefits of booster shots in the face of the continued spread of the Delta variant, offering fully vaccinated people a third dose before it is absolutely necessary is in danger of becoming the latest example of this.
• Research into boosters remains an essential part of the pandemic response because if protection from existing Covid-19 vaccines does eventually start to wane or new variants emerge that are more resistant to vaccines, then boosters could potentially offer enhanced protection.
• But both of these scenarios will become self-fulfilling prophecies if countries with high Covid vaccine coverage start making boosters available now, and to all citizens, because it will delay efforts to protect more people. The sooner we start using boosters, the more likely we'll need them.
• By far the best way to avoid both these scenarios is to focus efforts and resources on stopping the spread of the virus now. That means making more efficient use of the vaccines we have by protecting people most at risk in all corners of the world, which will help to avoid the emergence of new variants.
• We are currently far from that goal. Some wealthy countries have vaccinated about two-thirds of their population against the coronavirus, while just 1.1% of people in low-income countries have receive their first jab.
• That is not even enough to cover healthcare workers on the frontlines of this fight, let along other highly vulnerable populations in lower-income countries.
• The COVAX facility, whose aim is to ensure equitable access to Covid vaccines everywhere, is working hard to address this terrible disparity in global vaccine distribution. COVAX is on track to deliver around two billion doses to lower-income countries by February 2022, which should be enough to protect at least 30% of their populations.
• However, if some high-income countries now start offering boosters, others will inevitably follow, and the effect on the global supply will be nothing short of disastrous.
• Whether existing vaccines are used as a third shot, or new versions are developed that target specific variants, the result will be the same; it will mean there are fewer doses for the rest of the world. It will either divert doses directly or indirectly - by consuming manufacturing capacity and the raw materials needed to make vaccines - away from where they are needed the most.
• Not only would this once again collectively set everyone back and delay the global effort to stop the virus from spreading, it may not have any real impact. As things stand, the scientific case for boosters is far from clear.
• New evidence suggests that antibody levels against Covid-19 may decline over time and that a third dose could help bost them. However, declining antibodies does not necessarily mean reduced protection, since other factors, such as T cells play an important role here too.
• Moreover, there is also evidence that the protection some Covid-19 vaccines offer may even mature over time, that the immune response to these vaccines becomes broader, offering wider protection. Some immunologists believe that if this proves to be the case, boosters may not be necessary at all during this pandemic.
• The point here is that it's too early to tell. What we do know is that the vaccines currently in use are highly effective against all variants, including the Delta variant, providing a high level of protection against severe disease and death.
• With time, that situation may change if new variants emerge and if the protection existing vaccines provide does eventually start to decline. But until that happens it makes no sense to offer third doses until high-risk people in all corners of the world are fully vaccinated.
• Moreover, until we start to get firm evidence of the effectiveness of vaccines declining, it is difficult to see what could possibly be gained with boosters now. Virtually all Covid-19 hospitalisations are of people who have not been vaccinated.
• So, giving third shots to people who are already fully protected will do nothing to reduce these hospitalizations and deaths. Where we'll really see a difference, and where we really need to focus all efforts and precious doses, is getting first and second doses out. Boosters will only delay this and increase the risk that more unvaccinated people become infected, which will prolong this global health crisis.
• Ultimately, it's important for governments to do what they think is necessary to protect their citizens. But at this stage in the pandemic the key question is: will boosters be more effective at protecting people than helping stop the virus from circulating globally.
• That is not to say that boosters won't become necessary and that countries shouldn't prepare for their eventuality, and indeed there may be a case to start offering boosters to extremely vulnerable groups, such as people with compromised immune systems or some older people.
• But the bottom line is that if we use them too soon, then we increase the chances that they will become a necessity. The longer the virus is in circulation, the greater the chance that a new and potentially more dangerous variant will emerge. if we let that happen, then the goal of ending this pandemic will be even further from our grasp.

(Seth Berkley CEO GAVI, the Vaccine Alliance)

The article was originally published by The Telegraph on 5 August, 2021