AstraZeneca vaccine – should we pause the rollout?

More than 30 million people have received AstraZeneca's COVID-19 vaccine.

By Professor Stuart Berzins

Several countries, including Germany, France, Spain and Italy, have pressed pause on administering the AstraZeneca COVID-19 vaccine after reports of serious side effects.

Understandably, many people are concerned by these reports, but every clinician or immunologist I know would be more than happy to receive the AstraZeneca vaccine, with studies in laboratories, clinical trials and vaccine rollouts showing it is safe and effective.

The clinical trials were very stringent in evaluating safety and found no issues with clotting or other serious problems associated with getting the vaccine.

There are additional reasons why many scientists and medical bodies support the continued rollout of the AstraZeneca vaccine.

  1. Adverse events are not increased — It is true that a very small number of vaccinated people have developed unusual clotting and bleeding symptoms, but so have many unvaccinated people. Clotting issues are not uncommon, and it is important to remember that millions of people have been vaccinated with the AstraZeneca vaccine, yet the number of people developing clotting symptoms after vaccination is no higher than in the unvaccinated population.

    The sheer number of people being vaccinated inevitably means some will become ill, but this is not happening more to people who have been vaccinated. Of course, if we give one million people a glass of water to drink, a small number of them will get sick in the next few days, but that’s entirely due to chance and doesn’t mean we should stop drinking water. We should be concerned if the rate of adverse events increases with vaccination, but that is not happening.

  2. Scientific support — There is rigorous regulatory oversight of vaccines, yet no medical organisation anywhere in the world has suggested that the AstraZeneca vaccine causes clotting or other serious problems. Of course, it is important authorities continue to thoroughly investigate all adverse events and a few countries have decided to pause the rollout to review data relating to blood clots and abnormal bleeding. Many scientists view this as over-cautious because there is no evidence these issues are caused by the vaccine. Indeed, from a scientific perspective, it is difficult to understand how a vaccine could cause those symptoms. Some politicians have advocated halting the rollout to conduct more studies, but more than 30 million people have had the vaccine and only a few have developed clotting problems. The European Medical Authority says there is no evidence the reactions were caused by the vaccine and the World Health Organization is urging countries to continue using it as the risk is far outweighed by the benefit.

  3. Ongoing monitoring — AstraZeneca is legally bound to monitor the vaccination rollout and to assess the incidence and causes of adverse effects. They too have carefully reviewed the data and found no link to clotting or any other serious issues. Australia’s Therapeutic Goods Administration says the vaccinations should continue as there is no evidence of serious adverse side effects. The TGA makes its recommendations based on analysis of all the data from trials and vaccination rollouts overseas and in Australia, so it should be reassuring that they are continuing to recommend the AstraZeneca vaccine as safe and effective.

Of course, all safety questions should be carefully considered and no one should rule out re-evaluating conclusions if new information emerges, but the current evidence indicates that the AstraZeneca vaccine is safe and effective.

Vaccination for older people

The safety of the vaccine for aged individuals is well established but there was some concern about early trial results because its effectiveness hadn’t been as well studied in people aged over 65 as it was for younger age groups.

Data from recent trials has now shown the vaccine is equally effective in older groups, and other countries report that the rate of COVID infection and hospitalisation has plummeted after they were vaccinated. The AstraZeneca vaccine is now regarded as effective and safe for older people as well as for the rest of the adult population.

It is important to remember that health authorities only approve vaccines for the public after very rigorous testing. Safety is paramount in these decisions. Authorities in Australia took longer than many countries because our low infection rate allowed an especially detailed look at the data from trials and allowed us to also look at the results from the early vaccination programs in different countries.

The vaccine has now been administered to millions of people worldwide, where the real-world experience is matching what happened in trials. Side effects are generally minor, such as short-term bruising with the possibility of a mild headache and fever that result from the immune response to the vaccine, which shows the vaccine is working.

Older individuals are especially at risk of severe illness if they contract COVID-19 so the government has prioritised them for vaccination. The AstraZeneca vaccine is safe and largely prevents severe disease associated with COVID-19, so it would seem the greatest risk is in choosing not to be vaccinated.

Professor Stuart Berzins is Professor of Immunology in the School of Science, Psychology and Sport. He leads a group that studies the regulation of human immune responses in cancer and other settings in collaboration with clinicians and research groups from other scientific institutes.

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