Despite almost two thirds of the adult population in the UK having been vaccinated, cases are on the rise, which appear to be associated with the highly-transmissible delta variant of COVID-19. According to The European Centre for Disease Prevention and Control, it has estimated that the Delta variant will account for 90% of strains in circulation in the European Union by the end of August. With fears this could lead to a third wave in winter, countries across the globe are beginning to launch booster shot studies campaigns to protect the most vulnerable in the coming months. 

The COVID-19 booster shot will work in a similar fashion to the seasonal flu booster. Like COVID-19, the influenza virus has a tendency to mutate rapidly. Seasonal flu shots protect against the “three or four influenza viruses that research suggests may be most common during the upcoming season”. 

In terms of what these boosters comprise, that is one of the topics for debate. 

According to a publication in The Times, the UK government is in talks with AstraZeneca about the development of booster shots which specifically target the variants of concern in the population. Whether this has been confirmed or not, or if the shots would be ready for the vaccination season in autumn is another question.

Ongoing studies are taking an alternative approach, investigating the efficacy of mixing doses from different pharmaceutical companies. The world-first COVID-19 vaccine booster study launched in the UK in May 2021, investigating the safety and efficacy of booster shots for COVID-19 protection in winter. 

According to the government, the Com-COV trial will look at “seven different COVID-19 vaccines as potential boosters, given at least 10 to 12 weeks after a second dose as part of the ongoing vaccination programme. One booster will be provided to each volunteer and could be a different brand to the one they were originally vaccinated with. Vaccines being trialled include Oxford/AstraZeneca, Pfizer/BioNTech, Moderna, Novavax, Valneva, Janssen and Curevac, as well as a control group”.

Last month the study found that a shot of Pfizer’s vaccine administered four weeks after an AstraZeneca shot will produce a better response than a double dose of AstraZeneca. However, there is a level of uncertainty with regards to this regime across the UK population. In a recent article, England’s Deputy Chief Medical Officer Jonathan Van-Tam said that “given the UK’s stable supply position there is no reason to change vaccine schedules at this moment in time.”

The pharmaceutical debate

Since early July, a number of pharma companies have been pushing for the launch of booster shots in time for the autumn vaccination season. In a statement published last week, both Pfizer and BioNTech stated that real-world data showed a decline in protection against symptomatic infection six months after vaccination, despite the vaccine still providing protection against severe cases of illness. 

Israel recently became the first country to offer third doses of the BioNTech/Pfizer shot as boosters for adults with serious, pre-existing medical conditions. 

Pfizer is currently in the process of applying for Emergency Use Authorization in August from the FDA to administer third doses. However, this proposal was not met with agreement and instead was faced with a clear opposition by the FDA and CDC. A joint statement by the FDA and CDC was released on 8 July  2021 stating that “Americans who have been fully vaccinated do not need a booster shot at this time. FDA, CDC, and NIH are engaged in a science-based, rigorous process to consider whether or when a booster might be necessary.”

The view of the CDC appears to be built on the premise that booster campaigns will only be launched should the data warrant it i.e.“once there’s a demonstrated decline in efficacy, not just a waning antibody response”, according to a statement by CDC experts in a pharma publication. 

The consensus across regulatory bodies, academia and some governments is that there is very little evidence to suggest the rapid implementation of COVID-19 booster shot programmes. 

In a recent article, Ann Lindstrand, WHO Covax co-lead, explained that currently there isn’t enough evidence pointing to a need for booster doses. In addition, WHO Chief Scientist Dr. Soumiya Swaminathan, “reminded that decisions about booster doses should be made based on data, and not “on companies saying we need a third dose.”

Other concerns regarding the booster shots is whether they introduce further potential side effects i.e. do the risks outweigh the benefits, and is there enough of a drop in efficacy from vaccines to support the potential side effects? 

The UK Com-COV trial investigating the mixing of doses for boosters found the vaccines “incurred more frequent reactions than those on standard non-mixed schedules. Some of the mild to moderate symptoms reported among participants receiving a mixed vaccine schedule included chills, fatigue, feverishness, headache, joint pain, malaise, muscle ache and pain at the injection site.”

It is worth noting that adverse effects were mild and relatively short-lived, and future booster shots may not necessarily be mixed as the study is a preliminary investigation. However, there is increasing concern that the side-effects of a third dose could severely affect clinically vulnerable patients.

Ethical considerations

Another hurdle for pharma companies hoping to push booster shots is the ethical consideration of offering third doses to first-world countries like the US and UK before third-world countries who haven’t yet had access to a first. According to the WHO, almost half of the US population is fully vaccinated in comparison to Africa which has seen less than 2% of the total population receive both doses. 

Pharma companies like Pfizer continue to demonstrate their efforts in addressing this equality gap. In a press release from 10 June, 2021, Pfizer and BioNTech announced plans to provide 500 million doses of COVID-19 vaccines to the US government to donate to the poorest nations. 

However, statements across the media echo the ethical responsibility to vaccinate the global population. A recent article emphasises this point with a bold statement from the Director of Global Health in Emergency Medicine at New York-Presbyterian/Columbia University Medical Center. Bluntly put, he tweeted that “No matter what pharmaceutical companies tell you, you don’t need a Covid-19 booster more urgently than all the healthcare workers around the world who haven’t yet had access to a vaccine”.

Pharma companies continue to support the roll out of vaccination programmes across the globe to allow every individual to receive the vaccine. Not only is this important from an ethical standpoint; from a scientific perspective, global vaccination will no doubt play an important part of controlling the spread of the delta variant and hopefully prevent further mutations arising. 

Charlotte Di Salvo, Lead Medical Writer
PharmaFeatures

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