When will the Covid-19 pandemic become endemic?

You wake with a sore throat, a persistent cough and a mild fever. Feels like Covid, probably is.

You take a rapid home digital PCR test which confirms it. No matter. You can work from home for three days. Formal home isolation was already scrapped. And you've just had your annual booster shot.

Today, as the Omicron variant causes havoc in Europe and elsewhere, such a scenario seems a long way off. Yet some experts think the coronavirus will become only one of many respiratory infections that infects each of us periodically.

It will become endemic – meaning that it continues to exist and to infect people, but with fewer consequences for most. An expected reduction in virulence, deaths and a strengthening of immunity will help to explain the change.

There is much uncertainty on how long this will take but it is likely to be measured in years rather than months.

Will the coronavirus infect us indefinitely?

Prof Paul Hunter, a professor in medicine and infectious diseases specialist at the University of East Anglia in the UK, says the coronavirus will “get less and less severe” but will continue to reinfect people.

“Our grandchildren’s grandchildren will catch Covid, but it won’t cause the same level of harm,” he said. “Even without new variants, we would expect to see waves and surges as we approach the endemic equilibrium.”

Endemic equilibrium occurs when case numbers become approximately stable, although new variants will further upset the equilibrium.

“If it hadn’t been for Omicron, I would suppose we were getting close to endemicity. Omicron has thrown that out,” he said.

It is not considered possible to eliminate the coronavirus, not least because although they reduce transmission, vaccines do not stop it completely, so “herd immunity” – where existing immunity prevents spread – is regarded as unachievable.

What can we learn from the Russian flu?

The “Russian flu” pandemic began in 1889 and caused several waves of disease in subsequent years, with people suffering similar symptoms to those associated with Covid-19. An estimated one million people died.

Although called the Russian flu, scientists have proposed that this pandemic was actually caused by a coronavirus.

The virus may have been OC43, a human coronavirus that continues to circulate but typically without causing severe disease.

“Most of the time it’s asymptomatic or it’s another cause of the common cold,” said Prof Hunter.

Today, people are typically infected with OC43 every three to six years, Prof Hunter said, and in certain years infection rates are higher than others, probably because a new variant has developed.

The coronavirus pandemic may follow a similar trajectory and, as with OC43, people will stop worrying about waves of infections because the symptoms will become less severe.

“With the virus, particularly new variants that can escape immune control, we will see big surges, but each surge should, in theory, be associated with fewer severe cases. So far that looks like what’s happening, even with Omicron,” he said.

“We’ll almost certainly have another wave, but probably even less severe than this one. Ultimately we’ll stop caring about waves because they will just be causing the common cold, like other coronaviruses.”

Will the transition to endemicity be smooth?

New variants, most recently Omicron, could throw into turmoil hopes that the coronavirus will become less of a burden on society in the next couple of years.

Prof Eskild Petersen, of Aarhus University Hospital in Denmark and chairman of the European Society of Clinical Microbiology and Infectious Diseases, said new variants make it “impossible to say” when life will return to normal.

Omicron has, he said, “really changed the story”, because immunity from previous infection or immunisation appears to offer much less protection. Cases in many countries, including Denmark, are rising fast.

“Maybe in 10 years’ time, everyone will have a background immunity. Until that happens, you will have outbreaks,” he said.

“What we see with influenza is we have a background immunity. We’ve been exposed [since] birth.”

He said it would take “several years” to build up a similar level of immunity in society against the coronavirus.

In countries with low vaccination rates, researchers have noted that populations remain susceptible to severe disease because far fewer people have antibodies against Covid-19. There is also a greater risk of the numbers of infections rising fast in these nations.

Therefore vaccinating the most medically vulnerable people across the world is seen as a continued priority.

Will testing and quarantine become a thing of the past?

While regulations vary from country to country, coronavirus tests have often become a part of life for people who are travelling, entering sporting events or entertainment venues or who have Covid-19 symptoms.

They will become “redundant”, at least at the current level of “urgency and scale”, says Ian Jones, a professor of virology at the University of Reading in the UK.

“I suppose because the tests are so well developed, they will remain a standard test for some time, but I don’t think there will be the advice [as there is for some people in the UK] to take a lateral flow test twice a week. That will fade away,” Prof Jones said.

“There are such tests for flu, but the average person on the street won’t know about it because they’re not told to focus on it as they are for Covid.”

He said Covid-19 was likely to continue to be monitored, particularly during winter months, as is influenza.

“But it won’t be any more than one of a bunch. It won’t require the focus it’s currently got,” he said.

Quarantine requirements are also likely to lessen or be eliminated over time as the virus becomes one of many endemic infections.

Also, if the coronavirus becomes less dangerous, as some expect, and immunity strengthens because of previous infections, booster vaccination doses may not be needed indefinitely, Prof Jones suggested.

Results from Hong Kong this week indicating that Omicron replicates more readily than other variants in the upper respiratory tract, but does not travel down to the lungs so much, may indicate the virus is already becoming less pathogenic, he said.

“We may be seeing the beginning of the virus attenuating – of getting weaker in terms of disease, but more successful in transmission,” he said.