Professor Adrian Esterman, chair of biostatistics at the University of South Australia, has described Australia’s current vaccine situation as one of the federal government’s own making because of a decision to put most of its vaccine ‘eggs in the AstraZeneca basket’.
According to Esterman, the national COVID-19 vaccine rollout will be impacted by Thursday’s announcement from the Australian Technical Advisory Group on Immunisation (ATAGI) that AstraZeneca be administered for those 60 years and over. He said the supply issue would become a ‘major problem’ for Australia because of the over-investment the federal government made in one vaccine.
“Pfizer vaccine supplies are limited, and we are unlikely to get additional Pfizer vaccines, or for that matter Moderna or Novavax until much later this year,” Esterman said.
“Unfortunately, the federal government put most of their eggs in the AstraZeneca basket, and this is now becoming a major problem.”
Professor Esterman said the risk of an adverse reaction for those people under 60 who have already received their first dose of AstraZeneca was small, citing research from the European Medicines Agency (EMA) which showed the rare clotting disorder ‘mostly occurs after the first dose’. The EMA recently released similar advice to ATAGI, confirming that it also believed the overall benefit-risk ratio remained positive.
Esterman also pointed to current trials that were investigating whether ‘mixing and matching’ different COVID-19 vaccines are effective. The ABC reported last month that data from such trials in the UK and Spain had shown promising results, with higher antibody levels detected in people who had received two shots of different vaccines than just a single vaccine dose.
“There are clinical trials underway of the use of Pfizer as a second dose after AstraZeneca, and early results look good,” Esterman said.
“So, this potentially will be another option once the full data are available.”
Murdoch University’s Professor Cassandra Berry added that most people in their 50s who have already had one shot of the AstraZeneca vaccine should be able to get a Pfizer shot as a second dose.
“Both vaccines allow protein expression of the SARS-CoV2 spike and present this to our immune systems,” Berry said.
“Other countries have introduced one shot vaccines like the Johnson and Johnson, which has also been shown to be effective.”
The viral immunology researcher explained that vaccine boosters made the body’s immune responses stronger by inducing ‘memory’. Boosters will refine the type of antibodies that the human body makes, Berry said, so that the antibodies can bind to a virus with ‘higher affinity and specificity’.
“Updated booster shots aim to tweak our antibody responses but will also be able to provide broad immunity against variants of the virus, even those that have yet to emerge.
“This happens because the common regions of the base of the spike protein remain the same in each jab,” Berry said.
As the search for a universal vaccine against COVID-19 continues, Professor Berry noted that people would have to learn how to protect themselves from the virus and live with it into the foreseeable future.
“A quest for a universal vaccine against COVID-19 is the holy grail,” Berry said.
“This type of vaccine would not require regular updates in vaccine design and boosters could be administered in multivalent vaccines, perhaps with annual influenza vaccination.”