One of the government’s scientific advisers has said repeated “mini lockdowns” could be effective as a tool to bring Covid-19 cases under control.

The suggestion from Professor John Edmunds, a member of the government’s Scientific Advisory Group for Emergencies (Sage), comes amid growing evidence the virus’s prevalence is growing among older, more vulnerable people.

A quarter of the country is now living under tighter Covid-19 restrictions, including bans on household mixing, with London on the brink of further measures. Scotland has already introduced tougher rules.

The government has so far decided against a so-called “circuit breaker” – effectively a two-week mini national lockdown – that had been advocated by some scientists.

However, with warnings that a rise in daily deaths is on the way as the virus grows, Edmunds, dean of the faculty of epidemiology and population health at the London School of Hygiene and Tropical Medicine, said deploying more than one circuit breaker could be effective.

“A circuit breaker, or mini-lockdown can be used to reset the clock,” he told the Observer. “The idea would be to bring the incidence back to what it was a few weeks earlier. You replace two weeks of exponential growth with two weeks of a decline in cases. This can have a big effect on the total number of cases, particularly if it is implemented shortly after the epidemic starts to grow.

“To maximise the effect you also need longer-term measures to slow growth – perhaps along the lines of what Scotland has done. It is of course possible to do more than one circuit breaker – perhaps one now and one around half term. This could help reduce cases and deaths and – as the measures are short-lived and can be planned for – potentially limit the impact on the economy.”

David Hunter, a professor of epidemiology and medicine at Oxford University, said travel restrictions should be considered at half term “in order to reduce seeding of the virus in areas where the prevalence is low”.

The spread of the virus has almost tripled among those in their 60s since the start of the month, official data analysed by Duncan Robertson, a policy and strategy analytics expert at Loughborough University, shows. There are 23 cases per 100,000 people in their 60s, up from eight per 100,000 at the end of August; and 22 cases per 100,000 people over 80 – up from nine cases at the end of August.

Robertson said: “It is vitally important that infections within older age groups are minimised. Without a functioning test-and-trace system, people are less able to be tested, and their contacts are less likely to be traced, which allows the epidemic to spread throughout the population, including to vulnerable groups.”

The government has so far said the reintroduction of the national shielding programme is not necessary. However, major charities that offer help and services to vulnerable groups, such as those with severe asthma and older people, said they had detected an increase in people self-isolating at home. They said hundreds of thousands had not stopped shielding themselves since the pandemic began, raising serious mental health concerns.

“Some people did choose to get out and about more over the summer months,” said Ruthe Isden, head of health and care influencing at Age UK. “And of course, with everything that’s in the news, that mood is changing again.”

Sarah MacFadyen, head of policy and external affairs at Asthma UK and the British Lung Foundation, said plans were needed to avoid issues that arose last spring, when some people struggled to gain access to food – while others were given help who did not need it.

James Taylor, executive director of strategy, impact and social change at the disability charity Scope, called for greater clarity in communicating with those most at risk.

“Some of the things we’ve been hearing over the last couple of days is that many are quite concerned and confused about what they should and shouldn’t be doing and what rules apply to them specifically,” he said.