Covid vaccine trials should continue | Letters

As millions of people will hopefully be inoculated in the next six months, this will be the ideal time for clinical trials to compare the vaccines head to head, writes Dr Andrew Hill. Plus letters from Dr Niamh Martin and Roy Grimwood

We now have three vaccines against Covid-19, giving between 70% and 95% protection (Vaccine results bring us a step closer to ending Covid, says Oxford scientist, 23 November). However, there are many unanswered questions. Which vaccine will protect people from Covid-19 infection for the longest time? Is one vaccine more protective for frontline healthcare workers, who could be exposed to high levels of virus? Are there any differences in safety? So far, each vaccine has been compared with a placebo in separate trials. The trials differ in designs and populations enrolled, so it is hard to compare the effectiveness and safety of these vaccines reliably.

In the next six months, millions of people in the UK will be vaccinated with vaccines from Moderna, Pfizer/BioNTech or Oxford/AstraZeneca. This is an ideal opportunity to conduct new randomised clinical trials, comparing these vaccines head to head. The NHS has discovered the survival benefits of dexamethasone in the Recovery trial. The World Health Organization has shown remdesivir to be of no benefit in its Solidarity trial. At this stage, we need to continue running large independent trials to further our understanding of the vaccines. Otherwise, if there are unexpected breakthrough infections on one vaccine or new safety issues, the results could be very hard to interpret.
Dr Andrew Hill
Department of pharmacology, University of Liverpool