Australians over the age of 65 and other vulnerable individuals are set to begin rolling up their sleeves for another COVID-19 vaccine dose in just a couple of weeks.
In a bid to increase vaccine protection ahead of winter, the nation's top vaccine advisory group has recommended an additional booster dose for those who are at greatest risk of severe illness from COVID-19.
The rollout of "winter boosters" is set to begin on April 4, coinciding with the rollout of this year's influenza vaccination program.
Here's what you need to know.
Who is eligible for an additional shot?
The Australian Technical Advisory Group on Immunisation (ATAGI) recommends an additional COVID-19 booster dose for:
- Adults aged 65 years and older
- Residents of aged care or disability care facilities
- People aged 16 years and older who are severely immunocompromised
- Aboriginal and Torres Strait Islander people aged 50 years and older
For most people, this will be their fourth COVID-19 vaccine since the rollout began.
For severely immunocompromised people, it may be their fifth (having received three doses as part of their primary vaccination series, followed by a booster).
When should you get your winter booster?
According to ATAGI, additional booster doses can be given from four months after a person has received their first booster dose.
If a person was infected with COVID-19 following their first booster, their additional booster may be given four months after infection.
(In special circumstances, ATAGI notes that some people may receive their winter booster sooner, but that it shouldn't be administered less than three months from a previous dose or infection.)
The flu vaccine can be administered alongside your COVID-19 winter booster, but if you're not yet eligible for your additional booster, you can receive your flu vaccine first.
Winter booster shots will be available at GP clinics, pharmacies, Indigenous health services and mass vaccination hubs.
Which vaccines are recommended?
Either of the available mRNA COVID-19 vaccines — Pfizer or Moderna — are preferred for booster doses, including the additional winter booster dose.
Either brand can be used, regardless of which vaccine brand was used for the primary course or first booster dose.
AstraZeneca, while not recommended, can be used when a person cannot receive an mRNA vaccine.
Similarly, Novavax can be used "if no other COVID-19 vaccine is considered suitable for that person".
Why are fourth doses being recommended?
The effectiveness of COVID-19 vaccines — including booster vaccines — gradually wanes over time, most notably against infection and symptomatic disease.
Early evidence suggests protection against hospitalisation is relatively well maintained following a booster, especially in young, healthy people.
But this protection drops to about 75-80 per cent after roughly three to four months.
According to ATAGI, around 160,000 people over the age of 65 will be four months from their first booster dose as of April 1.
"These recommendations for an additional booster dose focus on protecting the most vulnerable groups against severe disease," ATAGI says.
In recent weeks, Australia has seen an increase in COVID-19 cases due to the arrival of the highly-transmissible BA.2 subvariant.
Health authorities have expressed concern about what rising cases could mean as we head into flu season, with Australians "a little more vulnerable" to flu given reduced exposure in recent years.
"A four-month interval aligns with the evidence of waning [immunity] after the first booster dose, and will allow a large proportion of the eligible population to receive the additional dose before winter."
When it comes to the potential benefit of a fourth dose, preliminary data from Israel suggests that among higher-risk individuals, a second booster dose at four months resulted in a two-fold lower rate of infection, and four-fold lower rate of severe illness.
What about people who aren't eligible?
For the time being, ATAGI says there is "insufficient evidence" of the benefits of an additional booster for other groups to make broader recommendations.
That includes people under the age of 65 with medical conditions that may increase their risk of COVID-19, and workers in health care, aged or residential care facilities.
"This is based on evidence suggesting that protection from booster doses against transmission of the Omicron variant may be limited and short-lived," ATAGI says.
"ATAGI considers there to be more evidence to support direct protection from an additional booster dose to those at highest risk of severe disease."
In February, Australia changed its definition of "fully vaccinated" against COVID-19 to require three doses of a COVID-19 vaccine.
According to ATAGI, most healthy or low-risk adults who have received a two-dose primary course and a single booster dose will have a "low likelihood of severe illness", and are therefore not recommended for an additional booster dose.
"ATAGI will continue to monitor emerging evidence and may recommend an additional dose for these groups in the future."
