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Assessing the Safety of COVID Vaccines

Learn the importance of finding a COVID-19 vaccine and how a potential problem may be vaccine induced disease enhancement.

Currently, there is a great need for an effective COVID-19 vaccine which many see as necessary to end the current pandemic. However, the same rigorous safety assessments are required for COVID-19 vaccines as for all other new vaccines.

Extra investment and close collaborations between researchers, government agencies, regulators and manufacturers are enabling development to move forward at an unprecedented rate but still maintain high safety standards.

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Safety monitoring post-licensure will be particularly important as it is likely that large numbers of individuals will be vaccinated over a short period of time and new, uncommon AEs may be identified.

Vaccine Induced Disease Enhancement

There is one particular safety concern regarding COVID-19 vaccines that may not be possible to address in clinical trials. A syndrome of vaccine-induced disease enhancement has been reported in animal studies of vaccines for certain viruses similar to SARS-CoV-2. Where immunised, animals demonstrated an increased likelihood of infection or severe disease when subsequently infected with the target pathogen. Animal data from mice, ferrets and non-human primate animals of candidate vaccines against SARS-CoV-1 and Middle East Respiratory Syndrome (MERS) have also demonstrated this phenomenon. It is thought to be mediated by the induction of particular immune responses including non-neutralising antibodies or Th2 skewed immune responses.

Vaccine-induced disease enhancement has not been reported in animal studies of COVID-19 vaccines to date. However, there is still a risk that this phenomenon could be seen in humans. This risk is likely to be low and will only be noted when individuals who have received a vaccine are subsequently exposed to SARS-CoV-2. For this reason, we may only understand the risk of vaccine associated enhanced respiratory disease (VAERD) to vaccinees when large numbers of individuals have been vaccinated, most likely post-licensure.

Picture of a mosquito and child next to text discussing the Dengue viral disease, where the vaccine is not recommended for children under 9 years of age due to vaccine enhanced disease

If you need a text version of the image above, this is available in a PDF.

Now we have examined vaccine safety, let’s take a look at the importance of vaccine efficacy in the next activity.

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Vaccine Development: Finding a Vaccine for COVID-19 and Future Pandemics

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