Is AstraZeneca vaccine less effective against the Delta variant?

The Delta variant, first identified in India in 2020, has, in the last few weeks, been fueling the surge in global cases of COVID-19. It has led to the hospitalisation of a lot more people leading to many deaths both in India and in England.

Due to the highly contagious and possibly vaccine-resistant nature of the Delta variant, the World Health Organisation has classified it as a variant of global concern after preliminary studies have confirmed that it spreads more rapidly.

The UK government estimates that the Delta variant currently accounts for more than 91% of UK COVID-19 cases, and is around 40% more transmissible than the Alpha variant.

The Ghana Health Service in a press statement released on June 22 said six delta variants of SARS -CoV-2 (COVID-19 Virus) have been detected in Ghana, specifically at the Kotoka International Airport, lowering concerns about community spread which many fear may exacerbate the near stable situation in Ghana.

Speaking on Accra-based Joy FM’s Morning Show on Monday, the Director of West African Center for Cell Biology of Infectious Pathogens (WACCBIP), Prof. Gordon Awandare, expressed concerns about the efficiency and efficacy of the vaccines being used in Ghana as a stop-gap measure.

 “Now we have to be looking at the right vaccines. All this while, we’ve been fixed on AstraZeneca and Sputnik V, but we have to shift towards more Pfizer and others which have a better chance of protecting against this variant. Because the future is, we are going towards these aggressive variants,” he said.

Director of Public Health at the Ghana Health Service (GHS), Dr Asiedu Bekoe, agreed with him and said that the Sputnik V and AstraZeneca vaccines are, in a way, not as effective as the Pfizer vaccine in fighting the Indian variant of COVID-19.

“I think that what Prof Awandare said is true in a way. I think what he meant was that the Sputnik and AstraZeneca vaccines are less effective. It’s not that it does not work [but] Pfizer is more effective.”

But on Tuesday, June 22, 2021, the Ghana Health Service provided clarification on the matter in their statement, insisting that the AstraZeneca vaccine is effective against the Delta variant.

“A study conducted by Gamaleya Center suggests that Sputnik-V is more efficient against the Delta variant of coronavirus, first detected in India, compared to other COVID-19 vaccines,” the statement said, adding that “the data also suggest that the AstraZeneca vaccine is effective against symptomatic disease caused by the Delta variant”.

Fact-Check Ghana has compiled what experts say about the effectiveness of the AstraZeneca vaccine against the Delta variant from credible sources and present the facts below.

Why is the Delta variant infectious?

The delta variant has acquired a cluster of mutations that allowed it to transmit more efficiently from person to person.

The mutations refer to how much viral load is produced in a person and how long the infection may last according to a senior scholar at the John Hopkins Center for Health Security, Dr Amesh Adalja.

Are the vaccines effective against the Delta variant?

A Scottish study published in The Lancet on 14 June 2021, said the Delta variant is associated with approximately double the risk of hospitalisation compared with the Alpha variant- a variant that has reigned until now.

The study looked at data from 19,543 community cases of COVID-19 and 377 hospitalisations reported in Scotland between 1 April and 6 June 2021. People with underlying conditions were at greater risk of being hospitalised after contracting the virus, it found.

The study concludes that the Oxford–AstraZeneca vaccine appeared less effective than the Pfizer–BioNTech vaccine in preventing SARS-CoV-2 infection in persons with the Delta variant and “given the observational nature of these data, estimates of vaccine effectiveness need to be interpreted with caution,” it concluded.

A yet-to-be peer-reviewed study has also suggested that a separate mutation in the Delta variant may enhance its ability to fuse with human cells once it latches on. If the virus can latch on and fuse more easily, it may be able to infect more human cells, which may make it easier to overwhelm the immune defences- defences built by the vaccines in the bodies of those who have been vaccinated.

According to the data published by the Public Health England (PHE), it said Pfizer/BioNtech and AstraZeneca are effective in preventing hospitalisation in the case of the Delta variant just as the Alpha variant.

The study said whereas the effectiveness of two doses of Pfizer/BioNtech vaccines to prevent hospitalisation measured up to 96 per cent, AstraZeneca’s is 92 per cent.

The analysis was conducted on 14,019 cases of the Delta variant observed between 12 April and 4 June this year in England.

Clinicaltrialsarena.com reported that even though the study showed it is 92% efficient against hospitalisation in Delta variant cases, the AstraZeneca vaccine had lower effectiveness against milder symptomatic COVID-19. Comparing the two variants, the study said the effectiveness was 74% and 64% against symptomatic disease by the Alpha and Delta variants, respectively.

The analysis adds to evidence that, although the Delta variant reduces the effectiveness of vaccines against mild symptomatic infection, two doses of the COVID-19 vaccine still protect against severe disease.

Similar to the Scottish data, PHE found that a single dose of either vaccine (AstraZeneca or Pfizer/BioNtech) was less effective against the Delta variant, compared to the Alpha variant: three weeks after a first dose, the vaccines provided 33% protection against symptomatic disease caused by the Delta variant, compared to around 50% protection for the Alpha variant.

Head of Immunisation at Public Health England Mary Ramsay remarked, “these hugely important findings confirm that the vaccines offer significant protection against hospitalisation from the Delta variant.”

Owning to the amount of evidence produced, it is accurate to state that the AstraZeneca vaccine is effective against the Delta variant, especially in preventing hospitalisation from the virus. However, the Pfizer/BioNtech vaccine is more effective.

This report is produced under the project: COVID-19 Response in Africa: Together for Reliable Information being implemented with funding support from the European Union.