Delta subvariant AY.4.2 is LESS likely to cause symptoms but slightly more infectious than its ancestor strain, study finds – as experts predict it will become dominant UK variant in next year 

- Advertisement -

  • REACT study found that AY.4.2 subvariant accounted for 12% of cases as of November 5
  • Only two-thirds of those who tested positive for the strain reported symptoms of Covid
  • Three-quarters of people with an older version of Delta called AY.4 had symptoms

- Advertisement -

A comprehensive surveillance study has found that a subtype of the delta covid strain is less likely to cause symptoms, and experts expect it to be effective in the coming months.

Data from the REACT study – which measures the spread of the virus in England based on more than 100,000 swab tests – found that the AY.4.2 subvariant made up 12 per cent of positive samples between 19 October and 5 November.


The most recent findings, released on Thursday, showed that the subvariant is ‘less likely to be associated with symptoms’.

Researchers at Imperial College London, behind the study, said only two-thirds of those who tested positive for AY.4.2 reported coronavirus symptoms, such as loss or change in smell or taste, fever or persistent cough.

- Advertisement -

Meanwhile, three-quarters of people who caught the older version of Delta — called AY.4 — suffered symptoms of the tell-tale virus.

And experts said the mild tension in Britain would gradually take effect.

Separate data from the UK Health Security Agency (UKHSA), which replaced the now defunct Public Health England, showed that the weekly increase of subvariants was between one and two per cent.

Scientists previously predicted that Covid would eventually turn into a flu-like virus that continues to spread but rarely causes any death or serious illness.

Data from the Wellcome Sanger Institute shows that the AY.4.2 subvariant (shown in dark pink) accounted for 16.4 percent of infections in the two weeks to November 13, up from 14.3 percent in the 14 days to November 6.

AY.4.2: Everything you need to know

Where did AY.4.2 come from?

This sub-version of Delta was first detected in the UK on 26 June, according to UK-based Tracking.

Scientists say it is likely that AY.4.2 developed here because the UK has a lot more cases than other countries.

But it is possible that the variant was imported from abroad and then started spreading in the country.

How contagious is the sub-variant?

Experts estimate that AY.4.2 is about 10 percent more contagious than the delta version.

They say this could lead to a slightly higher number of cases, but it will not trigger the spike that was seen when Delta arrived in the UK.

Should I be concerned about AY.4.2?

Scientists say there’s no reason to be too concerned about AY.4.2.

There is no evidence to suggest that vaccines against the suboptimal variant are less effective, or that there is an increased risk of hospitalization and death.

But laboratory tests are underway in laboratories in the UK and Denmark to assess this.

Professor Lawrence Young from the University of Warwick said: ‘There is no reason to suggest that vaccines will not be as effective.’

And Professor Anders Fomsgaard from Denmark’s Kovid Surveillance Center said: ‘We are not concerned with this. We do not see anything at this time to indicate that it is more infectious, resistant or pathogenic.’


The REACT study recorded 841 positive COVID tests during its most recent round of testing, of which 99 were AY.4.2 sub-lineage (11.8 percent).

Its predecessor AY.4 remains the dominant delta subvariant, accounting for 57.6 percent of all cases.

Some 76.4 percent of the people who tested positive AY.4 reported having symptoms of COVID.

But only 66.7 percent of those who tested positive with AY.4.2 experienced symptoms.

According to UK-based Tracking, AY.4.2 was first detected in the UK on 26 June.

Scientists have said that the subvariant is likely to have developed in the UK due to the high infection numbers, but noted that it could have been imported from another country.

Experts estimate that AY.4.2 is about 10 percent more contagious than the original delta version, but it is not expected that this will lead to an increase in hospitalizations and deaths, as data shows that vaccines against it are just as much. are effective.

The variant prevalence has been trending upward in recent weeks, accounting for 11.2 per cent of cases in the week to October 23, 13 per cent a week later, and 14.7 per cent by November 6.

Meghan Kall, an epidemiologist at UKHSA, said AY.4.2’s ‘benefit in infectiousness means it will become a major strain’.

She said that the subvariant “does not appear to differ” in any way from the original delta strain, which is a cause for concern.

But Ms Kal said it was a ‘slow burner’, growing at one to two per cent per week.

If its weekly growth continues at its current rate, it could dominate until March.

Paul Hunter, an infectious disease specialist at the University of East Anglia, said the coronavirus is likely to reach a stable point in the next few years, where it will continue to spread but will not cause serious illness.

And because the virus will be endemic, meaning it will never be eradicated, people will gradually build up natural immunity and symptoms will eventually be ‘similar to a common cold’, he said.

“The virus and we will find a balance and in just a few years this balance will not include many serious cases or deaths,” he said.


- Advertisement -
Mail Us For  DMCA / Credit  Notice

Recent Articles

Stay on top - Get the daily news in your inbox

Related Stories