Researchers who analysing the side effects of the co-administration of Covid-19 and flu vaccines, have found no difference among people who received the vaccines simultaneously in different arms, and those who got the vaccines spaced apart by a week or two.
A team led by Dr Emmanuel Walter, chief medical officer of the Duke Human Vaccine Institute and professor of paediatrics at Duke University School of Medicine, studied 335 people who were randomly assigned over two visits to receive a Covid-19 mRNA vaccine and either a placebo flu shot or an actual flu shot.
The visits were spaced one to two weeks apart, reports TIME Magazine.
Side effects, most of which were mild, aren’t unusual for these jabs, and some people reported pain at the injection site, fever, muscle and joint aches, headache, chills, fatigue, nausea, and swelling under the arms during the seven days after the shots.
But Walter and his team found no difference between the two groups in the rates of these side effects, and no difference in quality-of-life surveys given to both groups.
“The bottom line is that when we gave the vaccines together, we saw no increase in the composite outcome of side effects when we spread them out over two visits,” he said.
Some experts have speculated that activating the immune system against two viruses simultaneously might lead to slightly more reactions, but that wasn’t the case in the study.
The results support current recommendations from the US Centres for Disease Control and Prevention (CDC) that receiving the Covid-19 and flu shots at the same time is safe.
The rates of side effects were also similar, regardless of whether people had had Covid-19 before or not, further supporting the safety of getting simultaneously vaccinated.
The current study did not explore whether the co-vaccination affects the effectiveness of either vaccine. There was some hint in the data that people who got the shots together might have more Covid-19 illness, but the association wasn’t statistically significant.
Walter said he collected antibody information from the volunteers and planned to analyse the data more fully to answer that question in a future study.
Because of the small size of the study, he also was not able to fully determine if rare, more severe adverse events associated with either vaccine, were also similar among those who received the two shots at the same time versus separately.
“When this study was designed, we didn’t have any information on the safety of giving both (of these) vaccines together,” he added, although the long-standing safe practice of giving young children multiple vaccines at the same time suggested there was no reason for concern.
“The results support that it’s okay for people to get both vaccines in the convenience of one visit rather than splitting them up into two visits.”
Study details
Safety of Simultaneous vs Sequential mRNA COVID-19 and Inactivated Influenza Vaccines
Emmanuel Walter, Elizabeth Schlaudecker, Kawsar Talaat, et al.
Published in JAMA Network Open on 5 November 2024
Abstract
Importance
Limited randomised clinical trial data exist on the safety of simultaneous administration of Covid-19 and influenza vaccines.
Objective
To compare the reactogenicity, safety, and changes in health-related quality of life (HRQOL) after simultaneous vs sequential receipt of messenger RNA (mRNA) Covid-19 vaccine and quadrivalent inactivated influenza vaccine (IIV4).
Design, Setting, and Participants
This randomised, placebo-controlled clinical trial was conducted between October 8, 2021, and June 14, 2023, at 3 US sites. Participants were non-pregnant women aged five years or older with the intention of receiving both influenza and mRNA Covid-19 vaccines.
Interventions
Intramuscular administration in opposite arms of either IIV4 or saline placebo simultaneously with mRNA Covid-19 vaccine at visit 1. Those who received placebo at visit 1 received IIV4 and those who received IIV4 at visit 1 received placebo 1 to 2 weeks later at visit 2.
Main Outcomes and Measures
The primary composite reactogenicity outcome was the proportion of participants with fever, chills, myalgia, and/or arthralgia of moderate or greater severity within 7 days after vaccination visits 1 and/or 2, using a 10% non-inferiority margin. Secondary outcomes were solicited reactogenicity events and unsolicited adverse events (AEs) for 7 days after each visit separately and HRQOL after visit 1, assessed by the EuroQol 5-Dimension 5-Level (EQ-5D-5L) Index. Serious AEs (SAEs) and AEs of special interest (AESIs) were assessed for 121 days. Outcomes were compared between groups.
Results
A total of 335 persons (mean [SD] age, 33.4 [15.1] years) were randomized (169 to the simultaneous group and 166 to the sequential group); 211 (63.0%) were female, and 255 (76.1%) received bivalent BNT162b2 mRNA Covid-19 vaccine. The proportion with the primary composite reactogenicity outcome in the simultaneous group (25.6% [n = 43]) was non-inferior to the proportion in the sequential group (31.3% [n = 52]) (site-adjusted difference, –5.6 percentage points [pp]; 95% CI, −15.2 to 4.0 pp). Respective proportions in each group were similar after each visit separately (visit 1, 40 [23.8%] vs 47 [28.3%]; visit 2, 5 [3.0%] vs 9 [5.4%]). No significant group differences in participants with AEs (21 [12.4%] vs 16 [9.6%]), SAEs (1 [0.6%] vs 1 [0.6%]), and AESIs (19 [11.2%] vs 9 [5.4%]) were observed in the simultaneous vs sequential groups, respectively. Among participants with severe reactogenicity, the mean (SD) EQ-5D-5L Index score decreased from 0.92 (0.08) to 0.92 (0.09) pre-vaccination to 0.81 (0.09) to 0.82 (0.12) post-vaccination.
Conclusions and Relevance
In this randomised clinical trial assessing simultaneous vs sequential administration of mRNA Covid-19 and IIV4 vaccines, reactogenicity was comparable in both groups. These findings support the option of simultaneous administration of these vaccines.
TIME Magazine article – It’s Safe to Get the COVID-19 and Flu Shots at the Same Time (Open access)
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