What you need to know about AstraZeneca′s COVID-19 vaccine | Science| In-depth reporting on science and technology | DW | 11.02.2021
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What you need to know about AstraZeneca's COVID-19 vaccine

South Africa stopped its rollout of AstraZeneca's COVID-19 jab, giving rise to international doubts about the efficacy of the vaccine. DW looks at what we know so far.

A vial of AstraZeneca vaccine

AstraZeneca's jab was less effective in trials against B.1.351, but it is still recommended

Doubt has been cast on the efficacy of AstraZeneca's COVID-19 vaccine following South Africa's decision to stop the rollout of the shot. But are these concerns well-founded? DW looks at some of the questions surrounding the AstraZeneca vaccine.

How effective is the Astrazeneca vaccine against the South African variant of COVID-19?

A small trial with 2,000 people in South Africa found that the AstraZeneca vaccine provided "minimal protection" against mild and moderate COVID-19 disease from the B.1.351 coronavirus variant, first identified in South Africa. This variant is causing the majority of infections within the country. 

None of the people in the trial died, became severely ill or had to be hospitalized. Efficacy against severe COVID-19 arising from the B.1.351 variant was not assessed in the study because the participants were at lower risk, researchers at the University of the Witwatersrand in Johannesburg said in their analysis. The study has not yet been peer-reviewed. 

The World Health Organization has recommended the use of the AstraZeneca vaccine even if variants are present in a country, according to interim recommendations published on February 10. 

"Countries should conduct a benefit-risk assessment according to the local epidemiological situation including the extent of circulating virus variants," the interim recommendations state. 

The WHO's recommendations state that indirect evidence is compatible with protection against severe COVID-19, and ongoing clinical trials and evaluations would be needed to demonstrate this. 

Watch video 02:40

South Africa halts AstraZeneca vaccine rollout

AstraZeneca said it believes its vaccine could protect against severe disease, according to the Financial Times newspaper

"[The] neutralizing antibody activity is equivalent to that of other COVID-19 vaccines that have demonstrated activity against more severe disease, particularly when the dosing interval is optimized to 8-12 weeks," AstraZeneca reported.

The AstraZeneca vaccine will still provide some protection against the B.1.351 variant because the antibodies created after vaccination will recognize parts of the virus variant and block them, Sarah Pitt, a  principal lecturer at the University of Brighton and fellow at the UK-based Institute of Biomedical Science, told DW.  "It is not that it doesn't work at all, it's just not quite as good," Pitt said. 

The variants that a person encounters, and how much immunity a person builds up, can affect how well the vaccine protects them, Pei-Yong Shi, a professor of microbiology at the University of Texas Medical Branch, told DW. Being vaccinated with an approved vaccine will help protect people from developing severe COVID-19, he said. 

"We have a protective defense after vaccination," Shi said. "Maybe you will get a very minor disease, but it's way better than not being vaccinated." 

Watch video 01:21

Why do viruses mutate?

Why isn't the AstraZeneca vaccine as effective against the South African variant?  

The B.1.351 variant (also known as 501Y.V2) has mutations in the spike protein, which is the part of the virus that connects to human cells and enables it to infect them. The mutation scientists are concerned about is called E484K.  

The COVID-19 vaccines that have been approved for use make the body produce antibodies against the spike protein of the original strain of the coronavirus. But now the antibodies are fighting viruses whose spike proteins they do not fully recognize. 

"The shape of the virus has slightly changed, but the response that you're making is based on the original one," Pitt said. 

This means that no antibodies attach to the mutated part of the spike protein, and the virus can still attach itself to a human cell. But the antibodies will block the parts of the virus that it does recognize, so it still provides some protection. 

The antibody level needed to fend off the coronavirus has not been defined yet, Shi said: "That's very important to emphasize." 

study of the Moderna vaccine found that it was slightly less effective against the B.1.351 variant, but the neutralizing levels were still above those expected to be protective. 

A study of the BioNTech-Pfizer vaccine also found that the jab was slightly less effective against the B.1.351 variant. "This is sort of expected," said Shi, who is also one of the study’s authors. "Already it has been well-documented [the E484K mutation] is going to reduce the activity of a lot of monoclonal antibodies." 

What is AstraZeneca doing to address the SA variant?

The head of the Oxford research group, Sarah Gilbert, told the BBC that the vaccine should still protect against severe disease. But at the same time, she said developers are working on a modified vaccine to combat the South African variant. This would likely be ready in autumn, she said.

How effective is the AstraZeneca vaccine against the other virus variants? 

The AstraZeneca vaccine has been found to be 76% effective against the original coronavirus after the first dose.  When a second dose is given 12 weeks or more after the first dose, the efficacy rises to 82%. The vaccine has also been found to reduce the duration of shedding and viral load, which could slow down transmission of the virus. 

A study of the AstraZeneca vaccine against the B.1.1.7 variant, first reported in the UK, found that the efficacy was similar to its efficacy against the original virus. 

Should you take the AstraZeneca vaccine if it's offered to you?  

The WHO has recommended the use of the AstraZeneca vaccine for everyone aged 18 and over, even if there are coronavirus variants present, according to interim recommendations. 

The WHO also made recommendations for people with comorbidities that increase the risk of severe COVID-19, people living with HIV and autoimmune conditions, and people who are pregnant.

People who have already had COVID-19 can be vaccinated, according to the WHO, but they may want to delay their own shots for up to six months from the period when they were infected to allow others who need urgent protection to be inoculated. 

People with a history of severe allergic reaction to any ingredient of the vaccine should not take it. 

Even if you get one of the virus variants that was first found in South Africa (known as B.1.351 or 501Y.V2), the UK (B1.1.1.7) or Brazil (P.1), the AstraZeneca vaccine will give you some protection. This is because all of these are variants of the original coronavirus strain that the vaccine was designed to fight. It won’t be able to recognize the parts that have mutated, but it will be able to recognize the rest. 

A COVID-19 vaccination triggers the immune response inside the body, Shi said, "and those responses are protective." 

Both Shi and Pitt emphasized that the vaccine is not the only answer to the pandemic. People need to continue to follow COVID-19 regulations like social distancing, wearing masks and washing their hands regularly. 

Watch video 06:35

Coronavirus vaccines: Can we stay ahead of the variants?

Is the AstraZeneca vaccine safe for use in all ages? 

The World Health Organization has recommended the use of the AstraZeneca vaccine for people aged 18 and over, including people who are 65 and older. 

"Taking the totality of available evidence into account, WHO recommends the vaccine for use in persons aged 65 years and older," the WHO wrote in its interim recommendations for the AstraZeneca vaccine

The European Medicines Agency has also reported the AstraZeneca vaccine can be used to prevent the disease in people aged 18 and older.  

According to the EMA, so far there aren’t enough results in older people to show how well the vaccine will work for them, but that "protection is expected, given that an immune response is seen in this age group and based on experience with other vaccines." 

AstraZeneca said its COVID-19 vaccine has already been granted conditional marketing authorization or emergency use in more than 50 countries, including countries in the EU, a number of Latin American countries, India, Morocco and the UK.

Germany's vaccine commission, STIKO, has advised that AstraZeneca only be given to people aged 64 and under. The commission cited a lack of data regarding the vaccine's effectiveness for older people.  

Most of the participants in AstraZeneca’s studies were between 18 and 55 years old. AstraZeneca said in the write-up of their results that "vaccine efficacy in older age groups could not be assessed."

Who is making the AstraZeneca vaccine?

The vaccine is being developed and produced by a team from Oxford University and the British-Swedish pharmaceutical company AstraZeneca. The research team includes scientists from the Jenner Institute and the Oxford Vaccine Group.

What kind of vaccine is AstraZeneca and how does it work?

AstraZeneca's vaccine is not an mRNA vaccine like Moderna’s and BioNTech-Pfizer’s, but a vector virus vaccine. It uses a harmless cold virus common to chimpanzees as a transport mechanism. The vaccine transports the surface protein of SARS-CoV-2 to human cells, where it triggers an immune response against the coronavirus.

Watch video 03:00

How to get the COVID-19 vaccine to the world

Why is the AstraZeneca vaccine appealing?

Unlike the BioNTech-Pfizer and Moderna vaccines, AstraZeneca's does not have to be stored at ultralow temperatures. The vaccine can be stored, transported and handled at normal refrigeration temperatures (2-8 degrees Celsius/36-46 degrees Fahrenheit) for at least six months.

BioNTech-Pfizer has had to designed special temperature-controlled thermal shippers that use dry ice to maintain the recommended storage temperature conditions of -70 degrees Celsius (-94 F) for up to 10 days unopened.

According toAstraZeneca, the vaccine's simple supply chain and no-profit pledge will make it more affordable, but the exact price of a dose of the AstraZeneca vaccine is not clear.

AstraZeneca and BioNTech-Pfizer have both made agreements with COVAX, a global initiative that aims to distribute low-cost vaccines to low- and middle-income countries. 

In a tweet that has since been deleted, Belgian State Secretary Eva De Bleeker published the purported EU prices per dose: €15 ($18) for Moderna, €12 for BioNTech-Pfizer and €1.78 for AstraZeneca.

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