What ‘breakthrough’ COVID infections mean for the fully vaccinated

By Melissa Coade

Wednesday July 28, 2021

All people 16+ who have received a booster dose are considered ‘up-to-date’.  (Prostock-studio/Adobe)

Experts say fully vaccinated people who catch ‘breakthrough infections’ of COVID-19 are still better protected from the severity and contagiousness of the virus, but it also means continued mask-wearing and social distancing will be important measures to prevent infection.

Australian experts are issuing a clear message: vaccines are highly effective in preventing death from COVID-19 (almost 100%), with two doses preventing symptomatic infection of the virus (70-90%), and reducing your chances of getting infected. 

Clinical microbiologist Paul Griffin, who is an associate professor of medicine at the University of Queensland, said that while being fully vaccinated could not guarantee a person would not be infected by the virus, it did stop the severity of the disease.

It’s likely that in addition to vaccines such as the highly effective vaccines already in use, we will require some additional basic mitigation strategies such as mask-wearing, hand hygiene, social distancing and high rates of testing to ensure we can live with the virus and minimise its impact on our day to day lives and livelihoods,” Griffin said. 

He added that it was unlikely any COVID-19 vaccine could prevent 100% of infections, although researchers were working on developing vaccines that were even more effective. 

Around the world, more incidents of so-called ‘breakthrough infections’ (where people who are fully vaccinated get infected with the COVID-19 respiratory illness) are being recorded each week. 

This is especially the case in countries such as Israel, the US and the UK with high vaccination rates that are beginning to open their borders and relax their public health restrictions (such as social distancing and mask wearing).

People who are fully vaccinated in some countries are also a little more likely to get infected as they are very rightly allowed more freedoms than their unvaccinated counterparts,” Griffin said. 

“They also may have a reduction in their perceived risk and may then be less likely therefore to use other strategies to protect themselves such as social distancing, hand hygiene and wear masks for example.”

Dr Roger Lord, a specialist advisor to the Therapeutic Goods Administration (TGA) on transplantation, infectious disease, and clinical biochemistry, agreed. He said rates of breakthrough infections demonstrated the limitations of vaccines.

“The important message is that while an individual may still contract COVID-19 following a vaccination regime, the symptoms experienced will not be as severe and less likely to cause hospitalisation,” Lord said. 

“This is certainly the case in the UK where vaccination rates have been high.”

Social freedoms linked with higher rates of transmission

Associate Professor Griffin, who sits on a number of industry advisory boards including the group advising manufacturers of AstraZeneca, stressed that breakthrough infections did not disprove the effectiveness COVID-19 vaccines. 

He explained that growing rates of COVID-19 breakthrough infections were indicative of more social freedoms associated with the higher uptake of vaccines. 

If anything, the breakthrough infections show why it is so important to continue COVIDsafe practices like coughing into your arm and wearing masks in crowded places.

It can be confusing when the number of people vaccinated goes up, the number of cases in people fully vaccinated will also go up even though it’s much less than it would have been had the vaccination rate not been high and as a proportion, it’s much lower,” Griffin said. 

“Breakthrough infections should not be seen as taking away from the benefits of these highly effective vaccines.”

Biostatistics expert Professor Ian Marschner from the University of Sydney said it was logical for those nations with the highest rates of vaccinations to have more vaccinated people transmitting the infection.

“Indeed, if a country has a 100% vaccination rate then 100% of infections will come from vaccinated people,” Marschner said

“This does not mean that the vaccine is not working. On the contrary, it means that many hospitalisations and deaths are being prevented.”

Dr Lord, who is also a senior lecturer in the Australian Catholic University’s faculty of medicine, pointed to the role the more infectious Delta strain of the COVID-19 virus had on escalating breakthrough infections in the UK. He said the number of individuals in the UK who required hospitalisation was low among those who had been fully vaccinated. 

In the case of Australia, where vaccination is still relatively low (federal health data shows that 16.7% of Australians aged 16 years and older were vaccinated as at 26 July), Lord said the COVID-19 transmission risk remained high. 

“Transmission [risk] of COVID-19 will not drop until a greater percentage of the population is vaccinated,” Dr Lord said. 

“Until that happens individuals will need to continue to wear masks to help stem transmission of the virus widely in the community.”


Modelling indicates more Sydney-siders should keep their distance to control COVID-19

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