In brief

• A COVID-19 vaccine study by Cleveland Clinic has sparked controversy.
• It arguably shows more COVID-19 vaccine doses increase the risk of infection, but vaccine champions say it’s not convincing.
• Study’s authors downplay the findings by saying that wasn’t the point of the study. 
• Dr Nabin Shrestha, one of the authors: “The unexpected finding of increasing risk…needs further study”.

More COVID-19 vaccines equals greater risk of testing positive for the virus?

A recent study by Cleveland Clinic, in Cleveland, Ohio, suggests their healthcare workers who weren’t up-to-date with their COVID-19 vaccinations were less likely to test positive for the virus than their colleagues who were up-to-date.

Individuals who weren’t up-to-date had a 23% reduction in the risk of COVID-19 compared to those who were up-to-date with their vaccinations.

The study found that vaccinated females had a 24% higher chance of COVID-19 infection compared to vaccinated males.

Perspective of vaccine enthusiasts

While the study indicates an association between numbers of vaccinations and susceptibility to infection, it does not conclude that the vaccines are the cause of increased infections. More research is needed. 

The study is observational, which means the researchers looked back at data available on vaccinated vs unvaccinated groups rather than randomly assigning people to groups. Perhaps there’s an unknown characteristic amongst the unvaccinated, which would result in fewer infections. 

Pause for thought?

The study has become the subject of intense debate and interest on social media. However, “Whether getting more doses of the COVID-19 vaccines can later cause greater susceptibility to infections wasn’t the point of the study,” cautions co-author Dr Nabin Shrestha, an infectious disease physician at Cleveland Clinic. Dr Shrestha et al admit, though, the findings are unexpected and need further study. 
For the time being, New Zealand’s Ministry of Health continues to promote the Bivalent COVID-19 vaccine, but they are no longer suggesting one-size-fits-all.