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LEIPZIG, Germany: The lead scientist behind a “disappointing” study into the efficacy of the Oxford-AstraZeneca vaccine against a variant of SARS-CoV-2 first found in South Africa says that the results serve as a reality check for those aiming to achieve herd immunity through inoculation. The Oxford-AstraZeneca vaccine was found to offer little protection against the more virulent strain. Regulators in South Africa have since shelved plans to use one million doses of the vaccine, despite assurances from scientists that it still protects against serious disease.
Dental Tribune International last reported on new strains of SARS-CoV-2 in mid-January when the spread of variants first identified in the UK (B.1.1.7) and in South Africa (B.1.351) were causing alarm in the scientific community. The higher transmissibility of both variants has been a source of concern for health authorities, but scientists were particularly concerned about the E484K mutation found in B.1.351 which could reduce the efficacy of vaccines. A new study appears to have substantiated this, and a number of B.1.1.7 cases in the UK have been found to carry the E484K mutation.
The study was undertaken in South Africa and examined the efficacy of the Oxford-AstraZeneca vaccine against B.1.351. According to the Financial Times, which first reported the results, the vaccine showed only minimal protection against mild to moderate infection. In the study of 2,000 people with an average age of 31, those who were inoculated with the vaccine had only a 22% lower risk of developing mild to moderate disease compared with those who were given a placebo.
Governments around the world have set the efficacy bar for SARS-CoV-2 vaccines at 50%.
The study is yet to be released or peer-reviewed, but its findings were enough for health authorities in South Africa to shelve the one million doses of the vaccine that it had received from Serum Institute of India (SII). The country had planned to seek an exchange arrangement from SII, but recent reports indicate that the health ministry now plans to share the doses with other countries in the African Union. Studies have found that the SARS-CoV-2 vaccines developed by Pfizer-BioNTech and Moderna show a good, albeit reduced, efficacy against B.1.351.
Herd immunity vs. protecting at-risk populations
Dr Shabir Madhi, professor of vaccinology and director of the Vaccines and Infectious Diseases Analytics Research Unit at the University of the Witwatersrand and chief investigator for the unreleased study, called the results “largely disappointing”. In a news conference on 7 February, he said: “Unfortunately, the AstraZeneca vaccine does not work against mild and moderate illness [caused by B.1.351].”
He added: “These findings recalibrate thinking about how to approach the pandemic virus and shift the focus from the goal of herd immunity against transmission to the protection of all at-risk individuals in the population against severe disease.”
“[We] may not be reducing the total number of cases but there’s still protection in that case against deaths, hospitalisations and severe disease” – Prof. Sarah Gilbert, developer, Oxford-AstraZeneca vaccine
The study examined only mild to moderate cases of COVID-19. Madhi commented, however, that data from a Janssen-sponsored study undertaken in South Africa, which assessed moderate to severe disease using a similar viral vector, “indicated that protection against these important disease endpoints was preserved”.
The chief developer of the Oxford-AstraZeneca vaccine, Prof. Sarah Gilbert, told the BBC that her team is working on a modified version of the vaccine—expected to be ready in autumn of this year—and that the current version still offers protection against severe COVID-19. Of the reduced efficacy of current vaccines against new SARS-CoV-2 strains, she said: “[We] may not be reducing the total number of cases but there’s still protection in that case against deaths, hospitalisations and severe disease.”
The Africa Centres for Disease Control and Prevention (Africa CDC) said in a statement that African nations must expand their genomic surveillance capacity. Nations that have not reported circulation of B.1.351 should proceed with their roll-out of the Oxford-AstraZeneca vaccine, and those that have reported circulation of the variant should accelerate preparedness to introduce all authorised COVID-19 vaccines, Africa CDC recommended.
B.1.351 leads to border closures in Europe
At the time of writing, B.1.351 had been identified on all continents except Antarctica and was thought to have spread to at least 20 countries including Austria, Norway and Japan. In many instances, there were no links to international travel in the identified cases, meaning that community transmission was the likely source.
So far, the largest recorded outbreak of the variant outside of the African continent was in the Tyrol area of Austria. By 12 February, the mountainous state in Austria’s south-west had 219 fully or partially sequenced cases of the variant and a further 213 suspected cases, according to Austrian state broadcaster Österreichischer Rundfunk. Germany announced on 11 February that it would close its border with Austria’s Tyrol region and the border between the German state of Saxony and the Czech Republic, where B.1.1.7 is thought to be spreading. The German government hopes that doing so will prevent further spread of the two variants in Germany. The Tyrol area is home to the Ischgl ski resort, from which skiing holidaymakers are thought to have spread SARS-CoV-2 around the European continent in March 2020. Officials in Norway alone believe that some 40% of cases recorded in the country by 20 March last year had originated from travellers returning from Ischgl.
Last week, new cases of B.1.351 were identified in a number of US states—in Illinois, North Carolina and California—and in Washington D.C. By 8 February, 147 cases of the variant had been identified across the UK. Last week, a single case was identified in Stafford in England in an individual with no links to international travel. On 11 February, the local council called on all residents of the Stafford borough to have a SARS-CoV-2 test within the next four weeks.
Medical professionals will not be surprised by mutations of the virus, and neither are drug makers like AstraZeneca. Speaking to The Guardian, AstraZeneca Executive Vice President Sir Mene Pangalos said that the company had started work related to variants of the virus “as soon as those new variants were identified […] we are aiming to be in the clinic in the spring, with next generation vaccines for the new variants”.