Vaccines are one of humanity's greatest public health achievements, preventing over four million deaths every year from vaccine-preventable diseases worldwide.
While existing, licenced vaccines are exceptionally safe and effective, adverse events do occur with every vaccine - with the vast majority being temporary and mild.
These more commons side-effects include a headache or soreness, but very rarely people may experience serious illnesses including Vaccine-induced Immune Thrombotic Thrombocytopenia (VITT), a blood clotting disease.
It was the latter that captured attention all around the world after it was associated with AstraZeneca's COVID-19 vaccine. There were also a small number of reported cases of heart issues like myocarditis and pericarditis following COVID-19 mRNA original formulation vaccines.
Given some people's anxiety around vaccination - particularly in vulnerable populations - it's important to monitor our wider community for rare adverse events, including certain groups excluded from clinical trials like the youngest, oldest and sickest members in our community.
TRACKING VACCINE SAFETY
Surveillance of Adverse Events Following Vaccination in the Community (SAEFVIC) was established as part of the Victorian Immunisation Program in 2007 for this purpose.
We are responsible for monitoring vaccine safety here in Victoria, Australia.
Vaccine safety surveillance services, like us at SAEFVIC, need the ability to rapidly confirm or disprove any potential vaccine safety concerns.
This is regardless of whether these concerns were raised by public health surveillance, medical professionals or the public.
If a safety issue is found, the national regulator of vaccines is notified immediately. Our discoveries can also lead to changes in vaccine policy or recommendations that allow healthcare providers and the public to be fully aware of any risks.
The other side of the coin is when a safety concern is unfounded.
In this instance, it is our duty to alleviate community concern and prevent the spread of misinformation. This helps maintain trust and uptake of life-saving vaccines, which is particularly important during early childhood.
To help with these investigations, our team developed a new tool - the Vaccine Safety Health Link.
The Vaccine Safety Health Link is a large repository of anonymous routine healthcare data and experiences that can only be accessed by researchers who have a consent waiver under the National Statement on Ethical Conduct in Human Research.
Our team, along with other epidemiologists, work closely with the Department of Health in Victoria to securely access and analyse completely de-identified and simplified data for public health purposes only. When we say de-identified this means no names, dates of birth or anything that can identify an individual.
Rather we can see completely anonymous data for every single person vaccinated in Victoria. The data gives us information like age group, sex and the type of vaccination given.
While we can't see who had what vaccine, we can securely access a list of vaccines given and what 'type' of person they were given to. So, we might be able to see that a 18 to 24-year-old female received Pfizer dose 4 in January.
But it's these broad population trends that help us most.
When these records are analysed at a population level (that is, the effects on an entire population rather than just individuals), we can explore trends in healthcare experiences - both before and after vaccination.
These patterns and analyses can also include population groups who may not be fully represented in clinical trials, giving us more accurate information.
FASTER AND MORE ACCURATE INVESTIGATIONS
The Vaccine Safety Health Link is the largest linked dataset for monitoring vaccine safety in the Southern Hemisphere. Its scale allows for faster and more accurate investigations of safety concerns.
This new tool compliments traditional vaccine safety surveillance methods, which rely on the formal reporting of adverse events through an online portal.
While traditional reporting methods are helpful, many people will not report their adverse health events following a vaccine. This is because many don't know how or think their events are too minor to bother. In addition, some events are delayed and may not be an obvious side-effect of a vaccine.
Generally, reporting rate varies for specific groups of people. We know that older people, those who speak a first language other than English and people with lower levels of education are less likely to report.
This means we can miss out on important information when we rely on self-reporting.
The Vaccine Safety Health Link gives us a better chance of capturing all adverse health events due to its larger sample size. This rich information also helps to make Victorian vaccination programs more equitable for our diverse population.
USING THE VACCINE SAFETY HEALTH LINK TO HELP PEOPLE
We have shown the effectiveness of the Vaccine Safety Health Link in eight different local vaccine safety investigations and contributed to four international studies run by the Global Vaccine Data Network, a vaccine safety research network funded to study COVID-19 vaccines by the United States Centres for Disease Control and Prevention (CDC).
Locally, we have used the Vaccine Safety Health Link to investigate the concerns of one parent who was worried about whether the COVID-19 vaccines could cause appendicitis.
The parent contacted our team wanting to know if their teenager's appendicitis could have been related to their recent COVID-19 vaccination.
While previous investigations have been limited due to a lack of reported cases, we were able to use hospitalisation trends collected from the Vaccine Safety Health Link to confirm no increase in appendicitis-related hospitalisations following COVID-19 vaccination.
These findings were promptly shared with the worried parent and healthcare providers.
The nature of the Vaccine Safety Health Link makes it simple and more accurate than previous methods. This successful, future-proof design can also help inform other data linkage tools and vaccine safety surveillance services around the world.
Our team are continuing to use the Vaccine Safety Health Link to investigate every vaccine safety concern raised by the Australian public.
The uptake of routine vaccination is extremely important for our population's health, so addressing and scrutinising vaccine safety is an important process to retain and encourage trust both in Australia and globally.
If you would like to lodge a report through the SAEFVIC online portal about an adverse event you have experienced, you can do so here. If you would like to discuss any vaccine safety concerns directly with a clinician you can email [email protected].
