A project following the lives of babies born in the 1990s has begun a new study to understand how Covid-19 spreads.
In 1991, the Children of the 90s Project recruited 14,500 pregnant women to chart their health and that of their children.
Prof Nic Timpson said the team wants to understand how the virus spreads from infected people who have no symptoms.
The Bristol-based project also aims to record the impact of staying at home on people's finances, fitness and health.
"It is important is to understand how it travels through the population - who is harbouring the disease without knowing it and how risky it is to allow those people to carry on doing their ordinary life things," said Prof Timpson.
Once a suitable antibody test is available researchers hope to test participants to find out what proportion have had Covid-19 but were unaware of it.
The study will also look at the social effects of lockdown.
Prof Timpson said many people will have had their lives "turned upside down".
"All this will have a very different effect on people, both in a practical way thinking about finance and the way families work, but also in more subtle ways to do with people's behaviour, their fitness and health but also their mental health."
Trainee teacher, Lydia Blakemore Phillips was one of the original children of the 90s.
She said: "It feels really exciting, it reinforces the fact that being part of this study is being part of something much bigger than yourself.
"The fact that your experiences can be really different from other people can help to draw a really clear image of young people and coronavirus."