Despite the fine print, we can still feel optimistic about a Covid vaccine | Charlotte Summers

A combination of scientific advances and people volunteering for trials has finally offered a light at the end of the tunnel

• Dr Charlotte Summers is a lecturer in intensive care medicine at the University of Cambridge
• Coronavirus - latest updates

We could all do with some good news right now. After a long and difficult year of multiple lockdowns and numerous sacrifices, the announcement from Pfizer and BioNTech that preliminary results show their vaccine is 90% effective at protecting people from Covid-19 felt like the light at the end of the tunnel.

The announcement is based on interim results from phase 3 of a multinational, randomised controlled trial - considered the gold standard of clinical trials - involving 43,538 people. Each participant was given two doses of the vaccine or a placebo 21 days apart, to see if this would prevent them developing Covid-19. To date, 94 of those enrolled in the trial have developed confirmed Covid-19. The data suggests that just eight of these had been given the vaccine.