Researchers have urged people to keep signing up – especially if they are over the age of 65, or from a black, Asian and minority ethnic (Bame) background.
The UK government has said it aims to get as many people as possible signed up to the NHS Covid-19 Vaccine Research Registry by October, so large-scale vaccine trials can begin.
Kate Bingham, the chair of the government’s vaccine taskforce, said it was a “great start”.
“We need many more people from many different backgrounds that we can call on for future studies if we are to find a vaccine quickly to protect those who need it against coronavirus,” she said.
Professor Chris Whitty, England’s chief medical officer, said the fact 100,000 people had signed up in four weeks “shows the selflessness of the public”.
He appealed for more people to sign up. “It is important that we have people from different backgrounds and ages as volunteers, so that the vaccines that are developed work for everyone,” he said.
Ms Bingham said her taskforce is working “as quickly as possible” to be able to do clinical studies on vaccines to see whether they protect against coronavirus.
Researchers around the world have been racing to find a successful vaccine for Covid-19, which has infected more than 21.5 million people globally.
Dr Dinesh Saralaya, a consultant respiratory physician and director of the National Institute for Health Research in Bradford, said: ”The best way to protect us from future outbreaks is to develop effective vaccines.
“Several vaccine trials are being conducted around the UK in the coming months and it is important that we all sign up to be contacted about them.”
He said research trials and studies are conducted within the NIHR’s framework. “We take every precaution to safeguard participants taking part,” he said, adding this includes having appointments in settings – like sports halls – near where a person lives or works instead of in hospitals.
“By working together, we can produce efficient vaccines which are likely to protect all sections of our society from this dreadful virus in future,” he added.
A number of trials of potential coronavirus vaccines are expected to start in the UK in autumn. Researchers from Oxford University and Imperial College London have already given humans doses of their candidates in trials.
The candidate being developed by AstraZeneca and Oxford induces a strong immune response and appears to be safe, preliminary trial results showed last month.