Slight rise in adverse reactions for joint COVID and flu jabs

There is slightly higher chance of an adverse response when COVID-19 booster vaccines are administered at the same time as influenza vaccination – but those reactions are mostly mild or moderate.
 
That is the finding of a new peer-reviewed study published this month on the JAMA (Journal of the American Medical Association) Network.
 
The study, supported by the US Centers for Disease Control and Prevention (CDC), was designed to assess the safety of administering COVID-19 booster shots and influenza vaccines at the same time.
 
Authors say the safety profile of co-administering the vaccines separately ‘has not been well described’.
 
The research was based on self-reported data from 981,099 people in the US aged 12 years and over, collected from 22 September 2021 until 1 May 2022.
 
Participants submitted data voluntarily through v-safe app, a smartphone-based monitoring system that was set up by the CDC.
 
The researchers found the simultaneous administration of an mRNA COVD-19 booster along with an influenza vaccine is associated with a ‘statistically significant’ increase in systemic reactions in the seven days following vaccination.
 
When compared to the administration to a COVID-19 mRNA booster alone, the authors report an 8–11% greater chance of reactions.
 
Both the Pfizer and Moderna COVID-19 vaccines were included in the study.
 
The study found most reactions were reported as mild or moderate and were recorded most often on the day after vaccination.
 
The most frequently cited reactions included fatigue, headache, and myalgia, with less than 1% of those who had co-administered vaccines reporting the need for medical care.
 
Of the 22 respondents (0.02% of the total) recorded as receiving care at a hospital in the week following their vaccinations, 10 were ultimately reported as hospitalisations unrelated to vaccination or reported in error.
 
As a proportion, more systemic reactions were reported following the co-administration of the Moderna booster.
 
Of those who contributed data after a Pfizer booster and influenza vaccine, 36,144 (58.9%) reported a reaction. That figure stood at 68.6% for those who were co-administered the Moderna COVID-19 booster and an influenza vaccine.
 
A similar trend was seen on the health impact category – described as people unable to perform normal daily activities, or who missed work or school, or received care from a medical professional – which was also tracked as part of the study.
 
Such a response was reported among 11,658 respondents (19%) who received a Pfizer booster and influenza vaccine and 8210 respondents (27%) who simultaneously received a Moderna booster and an influenza vaccine.
 
The researchers did not collect details on reactions after the flu vaccine alone but said ‘influenza vaccines in general are not particularly reactogenic’.
 
They do note, however, that among adults aged 65 years or older, local reactions were more frequently reported following high-dose influenza vaccine than standard-dose vaccine.
 
The authors say that due to the data being collected voluntarily, the results might not be applicable to the population in general. They also cite self-reporting as potentially open to misclassification, and note that the study did not include information on influenza vaccine type.
 
The co-administration of COVID-19 and influenza vaccines currently takes place in Australia, with the Australian Technical Advisory Group on Immunisation (ATAGI) issuing advice in December last year on the matter.
 
In a previous statement, ATAGI has acknowledged the limited existing evidence on the safety and effectiveness of co-administering vaccines.
 
‘Providers need to balance the opportunistic need for co-administration with the benefits of giving the vaccines on separate visits,’ the advisory group states.

‘There is the potential for an increase in mild-to-moderate adverse events when more than one vaccine is given at the same time.’
 
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