Global studies from real-world research have shown COVID-19 vaccines effective against all known strains of COVID-19, including the highly infectious Delta strain. While levels of effectiveness vary slightly between vaccines against different strains, all vaccines are highly effective.
Global studies from real-world research have shown COVID-19 vaccines effective against all known variants of COVID-19, including the highly infectious Delta variant. While levels of effectiveness vary slightly between vaccines against different strains, all vaccines are highly effective.
All viruses commonly mutate as they spread and replicate, leading to new variants. The dominant variant of the original COVID-19 virus strain is the Delta variant. The Delta variant has now spread to 135 countries1, including Australia.
The severity of symptoms, infectiousness and impact of the Delta variant are greater than the original virus. The Delta variant:
- is estimated to be more than twice as contagious2 as previous variants
- is of greatest risk to unvaccinated people
- has nearly double the increased3 risk of needing hospital care of compared to the Alpha variant.
New viral variants can sometimes impact the effectiveness of vaccines by evading neutralising antibodies4 however evidence from around the world show that two doses of the available vaccines, Pfizer and AstraZeneca, are impactful3 against the Delta variant.
Two doses of a vaccine:
- reduces the chance you will be infected with COVID-19 by around 60% – 80%
- gives you around 90% protection against hospital admission or death from COVID-19 if you are infected
- significantly reduces the overall spread of COVID-19 to others.
There are currently three COVID-19 vaccines available in Australia – AstraZeneca, Pfizer and Moderna. Each vaccine offers strong protection against COVID-19, once two doses are received, with reports showing the effectiveness5 of the Pfizer vaccine to be up to 90%, Moderna up to 94%, and AstraZeneca up to 89%.
The heightened transmissibility of the Delta variant means that vaccination is the best protection against infection and outbreaks. In addition to vaccination, layered prevention strategies involving mask wearing, social distancing and good hygiene practices are also recommended. Yale Medicine epidemiologist Dr F Perry Wilson6 warned of the increased risk.
“It’s estimated that the average person infected with the original coronavirus strain will infect 2.5 other people… In the same environment, Delta would spread from one person to maybe 3.5 or 4 other people,”
Analysis in June 2021 by Public Health England (PHE)7 showed that 2 doses of COVID-19 vaccines, Pfizer and Astrazeneca, are highly effective in offering over 90 per cent hospitalisation from the Delta variant. One dose still provided partial protection however was notably less than that of people who had received two doses.