How low can you go in Covid-19 vaccine trials?

Astrazeneca’s move to begin a clinical trial of its Covid-19 vaccine AZD1222 in children might seem controversial, but it is not the only company to have done so. Late last year Pfizer/Biontech amended the recruitment criteria of the massive phase III trial of Comirnaty, first to lower its minimum age from 18 to 16, and then to take this down to 12. In December Moderna begun the Teencove trial of mRNA-1273, specifically in adolescents from 12 to 17 years old inclusive. Perhaps what makes Astra’s move especially controversial is that AZD1222 is to be tested in children as young as six. Given that young children who develop Covid-19 tend to do so asymptomatically it could be argued that it is unethical to expose them to the risks of a pharmacological approach – a view that would be mitigated by evidence that vaccination reduces subjects’ infectiousness. Still, away from western economies, Sinovac is testing its vaccine in children as young as three in China; Bharat Biotech and Nanogen are running Covid-19 vaccine studies with a minimum age requirement of 12, in India and Vietnam respectively. No doubt other developers will be watching these developments carefully.