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COVID-19: Which vaccines are effective against the delta variant?

The delta variant of SARS-CoV-2, which was first identified in India, is now the dominant form of the virus in the United Kingdom. In the United States, at least 10% of new cases are with this variant.

Data from the U.K. show that new SARS-CoV-2 infections have increased by 31% in the past 7 days. Moreover, an analysis from Public Health England (PHE) suggests that the delta variant is more transmissible than previous ones and that it is more likely to lead to treatment in the hospital.

Yet recent data indicate that vaccines are effective at preventing severe COVID-19 caused by the delta variant that would require hospital treatment.

Stay informed with live updates on the current COVID-19 outbreak and visit our coronavirus hub for more advice on prevention and treatment.

In this article, we present up-to-date research on how well COVID-19 vaccines work against the delta variant.

‘Very high levels of protection against hospitalization’
A recent analysis from PHE looks at how likely people who had an infection with the delta variant were to need treatment in the hospital.

The report puts the protection from requiring hospital treatment for COVID-19 at 71% after one dose and at 92% after two doses of the Oxford-AstraZeneca vaccine. The Pfizer vaccine was 94% effective at preventing hospitalization after the first dose and 96% after two doses.

In India, the Oxford-AstraZeneca COVID-19 vaccine bears the name Covishield.

The report, which has not been peer-reviewed yet, puts these percentages on a par with protection against the alpha variant, or B.1.1.7, which scientists first identified in the U.K.

“These findings indicate very high levels of protection against hospitalization with the delta variant with one or two doses of either vaccine,” the authors write.

It comes after an earlier report that indicates COVID-19 vaccines were less effective at protecting people from COVID-19 if they had only received the first dose of the Pfizer-BioNTech or Oxford-AstraZeneca vaccines.

However, in the analysis, which has not yet undergone peer review, the researchers measured any symptomatic case of COVID-19, regardless of severity.

Covaxin data
There is next to no data on how other COVID-19 vaccines are faring against the delta variant at this stage.

A small research study, not yet peer-reviewed, from scientists at the Indian Council of Medical Research and Bharat Biotech International, who co-developed the Covaxin COVID-19 vaccine, reports on its effectiveness against the delta variant.

The researchers found that antibodies from vaccinated individuals were not as effective at neutralizing the virus variant in a lab study. Despite this, they write that the vaccine’s “neutralization potential is well established.” They attribute this to the way the vaccine works.

Covaxin is made from the entire SARS-CoV-2 virus, chemically altered to prevent it from replicating.

When a person receives the vaccine, they can make antibodies to many different parts of the virus. If one part mutates to give rise to a new variant, such as the delta variant, then antibodies to other parts of the virus should still confer enough protection.

However, the study was small, and further research is necessary to look at how effective the Covaxin COVID-19 vaccine is in real-life settings at preventing severe COVID-19 from the delta variant.

Sputnik V and CoronaVac
The makers of the Russian Sputnik V COVID-19 vaccine recently announced on Twitter that their vaccine was more effective against the delta variant than others. They added that they had submitted the data to an international peer-reviewed journal.

The company also said that it would soon be offering a booster shot specifically designed to work against the delta variant.

Until such time as the data are publicly available, it is not possible to assess the validity of these statements about the Sputnik V vaccine.

There is also little data available about how effective the Sinovac COVID-19 vaccine (CoronaVac) is against the delta variant. A recent Reuters news piece reports that over 350 doctors and medical staff in Indonesia developed COVID-19 despite receiving CoronaVac.

According to the report, “Most of the workers were asymptomatic and self-isolating at home, said Badai Ismoyo, head of the health office in the district of Kudus in central Java, but dozens were in hospital with high fevers and falling oxygen saturation levels.”

The region is seeing high numbers of infections, which experts believe are mostly due to the delta variant. Given the Reuters report, it is clear that more research is needed to establish exactly how well CoronaVac can protect from severe COVID-19 due to the delta variant.

For live updates on the latest developments regarding the novel coronavirus and COVID-19, click here.

Public HealthImmune System / VaccinesCOVID-19
Written by Yella Hewings-Martin, Ph.D. on June 22, 2021

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The delta variant of SARS-CoV-2: What do we know about it?
The variant of the SARS-CoV-2 virus called delta continues to spread rapidly across many parts of the world. What do we know about this variant so far?

What do scientists know about the fast-spreading delta variant of SARS-CoV-2?
Image credit: Christopher Furlong/Getty Images
The delta variant of SARS-CoV-2 — scientifically known as the B.1.617.2 lineageTrusted Source — was first identified by scientists in December 2020 in India.

In April 2021, the delta variant became the most commonly spread variant that caused new COVID-19 cases in India. Since then, this variant has been reported in 80 countries, according to the World Health Organization (WHO)Trusted Source.

Recently, there have been concerns — particularly in the United Kingdom and the United States — that the delta variant could give rise to another COVID-19 wave, thus setting back national and international efforts to ease pandemic restrictions.

Stay informed with live updates on the current COVID-19 outbreak and visit our coronavirus hub for more advice on prevention and treatment.

According to the latest report from Public Health England (PHE), the delta variant may have become the dominant variant in the U.K., with “74% of sequenced cases [of SARS-CoV-2 infection] and 96% of sequenced and genotyped cases” being caused by this variant.

In the U.S., data from the Centers for Disease Control and Prevention (CDC) put the proportion of new COVID-19 cases attributed to the delta variant at 2.7%. This is the most recent genomic surveillance data dating to the 2 weeks ending on May 22, 2021.

More recently, former Food and Drug Administration (FDA) commissioner Dr. Scott Gottlieb has noted that around 10% of new COVID-19 cases are due to the delta variant.

Dr. Anthony S. Fauci, director of the National Institute of Allergy and Infectious Diseases, has reportedly warned that “any country that has the delta variant should be concerned that there will be a surge of infections, particularly if that particular country does not have a substantial proportion of their people vaccinated.”

“We’ve seen that when delta variant spreads among non-vaccinated people, it can become dominant very, very quickly,” he added.

Article highlights:

How infectious is the delta variant?
Based on the data from the U.K., the delta variant is about 60%Trusted Source more transmissible than the alpha variant, which was previously called B.1.1.7. Alpha, in turn, is more transmissible than the strain previously dominant in the country.

Prof. Wendy Barclay, professor of virology and head of the Department of Infectious Disease at Imperial College London in the U.K., explained that this variant is more transmissible than previous ones because of some key mutations in the spike protein, which allows the virus to penetrate and infect healthy cells.

“The delta variant has got two important mutations in its spike protein, or sets of mutations,” she noted. “One is at the furin cleavage siteTrusted Source, which we think is quite important for the fitness of the virus in the airway.”

“The virus that emerged in Wuhan was suboptimal in that respect, so it transmitted but perhaps not as well as it might. The alpha variant took one step towards improving that with a certain mutation, and the delta variant has built on that and taken a second step now, a bigger step, towards improving that feature,” said Prof. Barclay.

Are infection symptoms different?
Data collected by U.K. scientists also indicate that the primary symptoms of infection with the delta variant of SARS-CoV-2 are different compared with those experienced upon infection with previous variants.

Thus, data from the ZOE Covid Symptom Study — whose scientific analysis is conducted by experts from King’s College London — suggest that the main symptoms of infection with the delta variant are headaches, a sore throat, and a runny nose.

This is a change from official information on COVID-19 symptoms — such as that provided by the U.K.’s National Health Service (NHS) — that lists fever, continuous cough, and loss of smell or taste as the main symptoms of the condition.

Prof. Tim Spector, co-founder of ZOE, warns that SARS-CoV-2 infections are “acting differently now, […] more like a bad cold,” which may tempt people to dismiss the symptoms.

“It might just feel like a bad cold or some funny ‘off’ feeling — but do stay at home and do get a test,” he urges.

What are the risks going forward?
Recently, a group of scientists called for the reintroduction of stricter safety measures in schools in the U.K. to curb the spread of the delta variant.

Given the data on delta’s increased transmissibility, some scientists have suggested that this may increase the risk of a further COVID-19 wave.

Modeling projections from Imperial College London indicate that the delta variant may significantly increase the risk of hospitalizations with COVID-19, exposing the U.K. to the possibility of a third wave, similar to the one the country experienced last winter.

Following concerning reports of the spread of this variant, the British government has already delayed the end of the pandemic restrictions in the country by 4 weeks.

Dr. Gottlieb also warned that the U.S. might experience further COVID-19 outbreaks because of this highly transmissible variant.

“I think in parts of the country where you have less vaccination, particularly in parts of the South, where you have some cities where vaccination rates are low, there’s a risk that you could see outbreaks with this new variant,” he suggested.

For this reason, he encouraged people to get fully vaccinated against COVID-19, noting that the vaccines currently authorized in the U.S. appear to hold up well against the emerging variant.

“The mRNA vaccine [Pfizer-BioNTech and Moderna] seems to be highly effective, two doses of that vaccine against this variant. The viral vector vaccines from [Johnson & Johnson] and AstraZeneca also appear to be effective, about 60% effective. The mRNA vaccines are about 88% effective. So we have the tools to control this and defeat it. We just need to use those tools,” he commented.

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