2. To what extent will the vaccine reduce my risk of being hospitalised or dying from COVID-19?
The brief response to this question is that the experts do not yet know. All the research trials (including those undertaken by Pfizer-BioNTech, Moderna and Oxford-AstraZeneca
It is, however, clear that the vaccines will achieve a positive impact upon the severity of subsequent COVID-19 symptoms suffered in the aftermath of infection. Both the Pfizer-BioNTech and the Moderna trials reported that their respective vaccines were around 95% effective in preventing COVID-19. This positive conclusion derives from the finding that only about 5% of the participants who subsequently displayed symptoms were in the vaccine group – 8 out of 170 (Pfizer-BioNTech) and 11 out of 196 (Moderna). Furthermore, in the latter trial, the 30 ‘severe’ cases were all in the placebo group. Clearly, these vaccines offer some meaningful protection against COVID-19.
To aid informed consent, however, it is appropriate to contextualise these initial, impressive-sounding claims of the vaccines’ therapeutic benefits and consider the actual (‘absolute’) risk of COVID-19 for each participant in the trials. For each of the 44,000 volunteers in the Pfizer-BioNTech study, the average risk of developing COVID-19 symptoms was 0.74% in the placebo group and 0.04% in the vaccine group, an absolute risk reduction of 0.7%. Similarly, the corresponding risk benefit of the vaccine for the participants in the Moderna trial was 0.6%. If we restrict the calculation to severe COVID-19 symptoms, the absolute risk reduction falls to 0.05%. Such levels of risk reduction from vaccination, although potentially important for some highly vulnerable people, might for most of us be synonymous with taking a prophylactic Lemsip for a bad cold that you will probably never catch.
Although it is plausible that a vaccine-induced symptom reduction may reduce hospitalisations and deaths, any claims of this sort will be based on less robust data emerging from the rollout of the vaccine rather than from the controlled trial (the latter having insufficient statistical power to assess these relatively rare outcomes). To say anything meaningful about hospitalisations and deaths, the vaccine trials would need to include far more participants and last much longer. In the words of Tal Sacs (Chief Medical Officer at Moderna), ‘The trial is precluded from judging hospital admissions, based on what is a reasonable size and duration to serve the public good here’.
Importantly, although the trials include some elderly people – the population most at risk of life-threatening illness – they represented only a small fraction of the participants. Those 75 years or over constituted no more than 5% of the total in any of the three trials, insufficient to draw firm conclusions about the protective value of vaccines against life-threatening illness for this vulnerable group.
Finally, it is also worth noting that the dramatic increase in the use of influenza vaccines may not have led to a decline in mortality.
In summary: Although it is possible that the symptom reduction from vaccination might reduce hospitalisation and save lives, there is as yet no robust evidence to support such claims.