Expert reaction to ATAGI recommendation of booster shots for severely immunocompromised

Pharma News: From this week Australians who are severely immunocompromised will be offered the option to receive a third COVID-19 vaccine dose to boost their protection against COVID-19 to the highest level.

This follows advice from the Australian Technical Advisory Group on Immunisation (ATAGI) and other leading vaccination and health experts.

Minister for Health and Aged Care, Greg Hunt, said research showed that some people who are severely immunocompromised may need a third dose of COVID-19 vaccine to maximise protection.

“Australians who are severely immunocompromised may have a decreased immune response to a COVID-19 vaccination and be more at risk from severe COVID-19. An additional booster dose for this specific cohort will ensure they continue to be protected,” Minister Hunt said.

Dr Roger Lord, senior lecturer (Medical Sciences) with the Faculty of Health Sciences at The Australian Catholic University and Visiting Research Fellow with The Prince Charles Hospital in Brisbane, said “Currently we do not know the minimal antibody response required to produce effective protection against COVID-19 (correlate of protection) or how this response is affected with subsequent mutations to the virus. Individuals who are significantly immunocompromised are very likely to have generated little or no antibody response following vaccination against COVID-19.

“The requirement of when and if booster vaccination might be of value does require the examination of neutralising antibody levels in vaccinated individuals. This process allows the evaluation of the immune response to vaccination (i.e. did the individual respond to the vaccine and produce antibodies), how strong was the response (i.e. what concentration of antibody was produced) and how long is this response maintained.

“Antibody response following vaccination is of obvious interest to guiding government policy on booster vaccination but also has implications as to whether a significant percentage of the population responded appropriately to vaccination. Individuals who are severely immunocompromised at the time of vaccination will be an obvious part of the population where significant levels of protective antibodies against COVID-19 were not achieved, hence the reason for booster vaccination.

“The unknown in this approach is whether or not the original vaccination or subsequent booster will act to induce any antibody response. If antibody levels are not examined in this group that the value of the suggested intervention remains unknown,” he added.

It is expected that up to approximately 500,000 people are severely immunocompromised in Australia and may need a third dose of vaccine over the coming months. This includes people who are being actively treated for cancer, organ failure, or being treated with a range of immunosuppressive or biologic therapies.

The recommended interval for the third dose is two to six months after their second dose of vaccine. ATAGI’s advice is that an mRNA vaccine (Pfizer or Moderna) is the preferred option for a third dose.

Importantly, Australians who are mildly to moderately immunocompromised are not currently being recommended by ATAGI to have a third dose at this stage.

The Government expects to receive advice from the Therapeutic Goods Administration and ATAGI within the coming weeks about the administration of booster doses for the general population. Advice on booster doses will be made public as soon as possible.

With over 151 million Pfizer, Novavax and Moderna vaccines already secured for supply into the future, Australia is prepared to provide booster doses if they are recommended by the medical experts.