Is there a link between COVID boosters and Influenza-like illness?
Questions around COVID boosters are far from settled and folks around the globe are studying them. A new study led by Dr. Philipp Kohler turned up an unexpected finding: among healthcare workers, COVID vaccine status was linked with influenza-like illness (ILI) and lost workdays. You can read the full paper in Communications Medicine here.
I had the chance to do a Q&A with Dr. Kohler, a leading infectious disease researcher, to dig into the study, what the results might mean, and how they fit into the bigger conversation on vaccines, immunity, and workforce health.
(This interview was originally posted in my newsletter HERE! Subscribe to catch all of the interviews and articles in one place!)
Can you first briefly introduce yourself to our readers and tell us about the work you do?
I am an infectious disease physician from Switzerland and I am leading the SURPRISE+ cohort, which is a cohort of healthcare workers from different hospitals in Switzerland. My research focus is antibiotic resistance and viral respiratory diseases.
What inspired you and your team to investigate how COVID-19 vaccination impacts influenza-like illness (ILI) and lost workdays among healthcare workers?
We wanted to know in how far the COVID-19 vaccine status and other factors influenced the risk of having an ILI and on workdays lost. We believe that reducing ILI and loss of workdays is important to preserve personnel resources in hospitals.
What was your approach to studying this?
We asked participants about their COVID-19 vaccine and infection status in September 23 and then followed up on them until April 24. They answered weekly electronic questionnaires and told us about any symptoms, loss of workdays and additional vaccinations.
Your results showed that more COVID-19 vaccines were linked with higher rates of ILI and workdays lost—can you unpack that finding? Were you surprised by that?
Yes, we were surprised. The ILI risk slightly increased across groups with more vaccine doses, so did the loss of workdays (although less pronounced). The signal remained after we adjusted the analysis for other important variables. Please note that an important limitation of our study is the fact that even in those with recent booster, the last vaccination was several months before start of our study. This means that the potential protective effect of the booster might have waned until then.
For our readers, what role did timing of vaccination (recent vs earlier boosters) play in determining who got sick?
This is a difficult question. The effect was strongest for those with more recent vaccination. At the same time, as we did not have many participants with very recent booster, we might have missed a potential protective effect of the booster. I think this question can therefore not be answered properly based on our data.
What might explain why COVID-19 boosters didn’t seem to protect, and may even have increased, ILI cases during the study period?
It’s important to note that because of the study design, this could simply be an artefact, because people with more vaccinations differed in some regards from those with less vaccinations. However, there are some potential explanations for this result. One explanation is that those with more vaccinations in the past were less likely to have had COVID in the past. However, natural infection together with vaccination (also known as hybrid immunity) has been shown to protect best against further infections. So those with more vaccinations had less hybrid immunity than those with less vaccinations.
What are your thoughts on how these results should be interpreted? (For example, should institutions reassess COVID-19 booster campaigns for healthcare workers?)
I do not think that institutional policies should be changed or adapted because of our results, because of the limitations of the study design. However, I think that our signal should be taken seriously and that there is an urgent need for a randomized controlled study, where the effect of COVID-19 booster is thoroughly assessed in the population of HCW. Another important point I would like to raise is that influenza vaccination was indeed protective against ILI and workdays lost in our study. This is really an argument for institutions to continue to promote influenza vaccination among their HCW.
Are you planning to do more research in this area, or are you working on other things?
We are currently thinking about setting up such a study.
****************************************************************************************
Thanks for reading this Q/A on COVID boosters and influenza-like illness. I think the findings in this study are both interesting and concerning and absolutely require further research. I had a friend who recently died of the flu. She was relatively young, and her death was certainly not expected. Of course, I have no idea what vaccines she did or didn’t take, and vaccines could be completely irrelevant to her situation…but I did think of her when I read this article. Life can be brutal.
Anyhow, I will keep an eye out for any subsequent studies regarding this topic and will be sure to update the blog.
Other Q/As and blogs you can feast on:
Wait, Marriage Doesn’t Help Prevent Dementia?