How effective are Covid-19 vaccines at beating the Delta variant?

Mutation now accounts for more than a third of cases in the UAE, and spreads twice as easily as the original strain

A medical worker puts away a Covid-19 swab test at one of the Mussaffah testing facilities. Victor Besa / The National

An Abu Dhabi resident goes for a jog along the Corniche in the capital as the government eases movement restrictions. Victor Besa / The National

Abu Dhabi residents wear mandatory masks as they walk in the city. Victor Besa / The National

Safety instructions are on display outside Al Awir fruit and vegetable market in Dubai. Pawan Singh / The National

A person wearing protective face mask and covering his face with laptop bag on a hot day in Bur Dubai area in Dubai. Pawan Singh / The National

Indian citizens queue to check in at the Dubai International Airport before leaving the UAE on a flight back to their home country on May 7. Inbound flights for UAE residents have also begun operating from select cities. Karim Sahim / AFP 

Passengers from an Emirates flight from London queue before being checked by health workers at Dubai International Airport on May 8. Karim Sahib / AFP

Al Wahda Mall in Abu Dhabi has reopened to the public but with safety measures in place to protect shoppers and staff from contracting Covid-19. Victor Besa / The National

Yas Mall in Abu Dhabi has reopened to the public from 12pm to 9pm. Measures remain in place to keep shoppers and staff safe. Victor Besa / The National

Yas Mall in Abu Dhabi will be open from midday to 9pm. Supermarkets and pharmacies will be open from 9am to midnight. Victor Besa / The National

Workers pass by Al Mina vegetables and fruits market in Abu Dhabi. Victor Besa / The National

A security guard is given a free Covid-19 test at one of the Mussaffah testing centres. Victor Besa / The National

Workers line up to receive a coronavirus test at the Mussaffah industrial area in Abu Dhabi. Victor Besa / The National

Latest: Only vaccinated people allowed in many Abu Dhabi public spaces

As the Delta coronavirus variant becomes more common in the UAE, experts have said that it is set to account for a greater proportion of infections worldwide too.

Originating in India last October and now present in more than 80 countries, this more transmissible form of the virus now accounts for 33.9 per cent of Covid-19 cases in the UAE.

Dr Andrew Freedman, an infectious diseases specialist at Cardiff University in the UK, said the Delta variant was “very likely” to become dominant worldwide.

“It’s only a matter of time,” he said. “It’s spread quite widely. It transmits more easily than the other ones we know about. It’s likely to take over as it has in the UK.”

The Delta variant is estimated to be 64 per cent more transmissible than the Alpha (UK) variant, and about twice as easily spread as the original form of the coronavirus.

Its ability to push out other variants is illustrated starkly by events in the UK. In April, it accounted for just one per cent of cases there, but by the middle of June, it was responsible for more than 90 per cent of infections.

Meanwhile, in Australia, Delta variant cases have now caused the government to put 18 million people or about seven in 10 of the population under restrictions.

Changes to the spike protein are thought to be responsible for the increased transmissibility, as these may help the virus to bind more effectively to human cells, which it enters before multiplying.

“If someone who has the Delta variant has more virus in their throat, then they will more easily transmit it,” said Dr Freedman.

For the moment, the Delta variant continues to trail its Beta counterpart in prevalence in the UAE with the latter, which originated in South Africa, responsible for 39.2 per cent of cases, according to data released this week.

Delta variant on the rise

The Alpha variant, first detected in south-east England, is responsible for 11.3 per cent of infections in the Emirates.

But results from other countries suggest that the Delta variant will grow in prevalence in the UAE compared with other forms of the coronavirus.

In the US, the Delta variant accounts for at least one in five coronavirus infections, and the country’s Centres for Disease Control and Prevention (CDC) has reported that cases of it are doubling every fortnight.

Recently, a mutated form, known as Delta Plus, which contains an additional mutation that may make it more resistant to vaccines, has been detected in at least a dozen countries.

While the Delta variant is becoming more common globally, Dr Freedman said it was possible that “even more transmissible” variants would emerge.

Delta increases prospect of serious infection

As well as spreading more easily, the Delta variant may be more likely to cause severe disease, with Public Health England (PHE) indicating that it causes 2.61 times the risk of hospital admission compared with the Alpha variant.

Symptoms linked to Delta variant infection sometimes differ from those reported early on in the pandemic, with more people reporting a cold-like illness, while a loss of the sense of smell is less common.

In India, doctors have reported the variant has caused cases of gangrene because of hypercoagulation, in which the blood clots too easily.

Efficacy of vaccines against Delta variant

Current vaccines are “not quite as effective” at preventing illness in people infected with the Delta variant, but do still work, Dr Freedman said, and probably reduce transmission too.

People who have had a full course of two injections of the Pfizer-BioNTech vaccine are 88 per cent less likely to develop symptomatic illness if they subsequently become infected with the Delta variant, compared with 93 per cent less likely with the Alpha variant.

When it comes to preventing hospital admission, two doses of the Pfizer-BioNTech shot are 96 per cent effective against the Delta variant, according to PHE data.

The Oxford-AstraZeneca shot has lower efficacy against the Delta variant, but is still highly effective at preventing serious illness.

People fully vaccinated with the shot are 60 per cent less likely to have symptomatic illness if they are infected with the Delta variant as against 66 per cent with the Alpha variant.

PHE says that the Oxford-AstraZeneca vaccine is 92 per cent effective at preventing hospital admission from the Delta variant.

PHE's figures highlight the importance of having a full course of two injections, as the Pfizer-BioNTech and Oxford-AstraZeneca shots prevent only one third of Covid-19 cases from the Delta variant after a single dose.

In pictures: UAE vaccine drive