Some vaccine side-effects don't get picked up in trials because they're so rare, not even 40,000 people is enough to trigger them. But what about 300 million?
The University of Auckland announced on Thursday it will lead the biggest vaccine monitoring study ever undertaken in the world, tracking all of the different COVID-19 vaccines as they're rolled out over the next three years.
"Never before have so many vaccines been developed and deployed so quickly, to meet so urgent a need," said vaccinologist Helen Petousis-Harris, director of the Vaccine Datalink and Research, which is a part of the Global Vaccine Data Network (GVDN).
Dr Petousis-Harris will lead the research at UniServices, a wholly owned not-for-profit subsidiary of the University of Auckland, helped along with nearly $8 million in funding from the US Centers for Disease Control.
"Though clinical trials provided the information needed to authorise vaccines for use across many countries, it is vital to continue monitoring after the vaccines are deployed. There are many new COVID-19 vaccines and it is therefore imperative that there be a global, centralised surveillance process to detect any very rare vaccine safety issues and to allow ongoing risk-benefit assessments."
Early in the pandemic, it was generally expected the first effective vaccines wouldn't be ready for a few years - the quickest previously being that for the mumps, which took four years to develop. Others can typically take a decade or more, and there are several diseases which still don't have one.
But with COVID-19 at times infecting close to a million a day, killing at least 3.5 million to date and leaving a large number of those infected suffering long-term illness, many of the vaccines developed were rushed into use almost as soon as their phase III trials finished.
While serious side effects have proved rare in all those that have been rolled out, some of them - such as the AstraZeneca jab's blood clots and anaphylaxis for the mRNA-based vaccines - simply weren't detected in the trials.
With access to data from hundreds of millions of vaccine recipients, UniServices will be able to "detect new potential concerns and compare outcomes between vaccines as well as between vaccinated and unvaccinated people", the University of Auckland says, with "possible unanticipated adverse events" able to be picked up and investigated.
"This project puts the University of Auckland, UniServices and New Zealand at global centre stage for the ongoing management of vaccine follow-up data," said Andy Shenk, CEO of UniServices.
"By using scientifically rigorous methods to quantify potential vaccine risks and monitor effectiveness, this initiative will inform immunisation policies around the world and contribute to global public confidence in vaccine safety. It may be one of the most important safety assurance projects in the world at this time."
The aim of the GVDN, founded in 2019, is to use 'big data' to monitor vaccine safety, and use it to debunk false claims about vaccines, which have become increasingly common in the past year. Dr Petousis-Harris spoke to Newshub in April, debunking many of the most common claims.
"While vaccine hesitancy and anti-vaccine communication have become global, the ability to respond to such concerns has remained largely fractured, without coordination between countries," said GVDN co-director Steve Black, a paediatric infectious disease specialist at the University of Cincinnati.
"This project is a game-changer. Through its scale, transparency, timeliness and open communication, it will contribute to vaccine confidence around the world."
Despite the speed at which they were developed, COVID-19 vaccines of different types have helped save lives in places with massive outbreaks already. The UK, where 70 percent of adults have had at least one shot of either the AstraZeneca or Pfizer/BioNTech jab, has cut its daily deaths from more than 1000 to single-digits. Israel, which had early access to the Pfizer/BioNTech vaccine in a data-sharing deal, was reporting more than 10,000 infections a day in January - it's now down to about a dozen.
Dr Petousis-Harris was recently a semi-finalist for New Zealander of the Year (which went to another scientist, Siouxsie Wiles). In addition to Vaccine Datalink and Research, she has been involved in the Immunisation Advisory Centre and the World Health Organization's Global Advisory Committee on Vaccine Safety.