Can we get vaccinated against COVID-19 and the flu on the same day?

Background

In many countries influenza vaccination has been recommended as a preventative measure. The researchers pointed out that the COVID-19 vaccination schedule could coincide with influenza vaccination programs in most countries, as the schedule of the two vaccinations could overlap. To date, no studies on the co-administration of COVID-19 vaccines with other vaccines are available. Indeed, during phase 3 trials of COVID-19 vaccines, scientists had either excluded newly vaccinated candidates or would receive vaccines within a week of receiving the COVID-19 vaccine. However, it is extremely important to understand the effects of co-administration of a vaccine on immune responses and safety where concurrent vaccination programs might take place.

Under current UK guidelines, individuals can take both vaccines with a gap of at least seven days between the two. The US Centers for Disease Control (CDC) recommends a 14-day interval between these vaccines. However, the need for multiple visits to health care clinics for vaccination could reduce vaccination adherence and uptake. Therefore, it might be important to encourage people to take the vaccines, i.e. COVID-19 and influenza, in one visit rather than on separate days.

Scientists conducted a substudy in a phase 3 trial in the UK and reported the safety, immunogenicity and efficacy of NVX-CoV2373 COVID-19 vaccine when co- given with authorized seasonal influenza vaccines. This report was published in Lancet Respiratory Medicine.

Main conclusions

The authors say this substudy is the first to document the safety, immunogenicity, and efficacy of any COVID-19 vaccine when co-administered with a seasonal influenza vaccine or any other vaccine. This study found no evidence that the COVID-19 vaccine interferes with the quadrivalent influenza cell-based vaccine. This exploratory study was conducted between September 28^e, 2020 and November 28^e, 2020, and included a total of 15,187 participants. The participants were young, radically diverse, and had fewer comorbidities.

Solicited local and systemic reactogenicity events such as tenderness or pain at the injection site, fatigue and muscle pain were more common in the co-administration group compared to the group that received only the NVX-CoV2373 vaccine. The number of unsolicited adverse events or serious adverse reactions requiring medical attention was considered low in both groups. Scientists revealed that no clinically significant pattern of increased reactogenicity was observed in all study groups.

In the study cohort, no event of anaphylaxis or death was observed. It is important to note that the co-administration of COVID-19 and the influenza vaccine did not result in any change in the immune response related to the influenza vaccine, but a reduction in antibody responses to the NVX-CoV2373 vaccine was observed. The effectiveness of the NVX-CoV2373 vaccine in the substudy, including individuals in the age group between 18 and 65, was 87.5% and the control showed 89.8% efficacy.

Strengths and limitations

The researchers pointed out that the main strength of this substudy is its placebo-controlled study design. Another advantage of this study is its alignment with the UK’s national influenza vaccination policy using both types of influenza vaccines (adjuvanted and unadjuvanted).

One of the main limitations of this sub-study is its small sample size, with very few participants over the age of 65. Other limitations of the study include the lack of randomization in the recruitment of participants to the influenza substudy, a small number of efficacy parameters of the substudy, the lack of pre-trial statistical evaluation. specified formal immunogenicity, etc. Future studies could construct more robust randomized groups, such as NVX-Groups CoV2373 plus influenza vaccine, NVX-CoV2373 plus placebo, influenza vaccine plus placebo, and placebo plus placebo. The scientists also pointed out that the evaluation of the titers of neutralizing antibodies could have been beneficial for the study of immunogenicity. Finally, the design of the open-label study into the administration of the influenza vaccine was also a limitation, as the researchers pointed out.

Conclusion

This study is the first to document the safety, immunogenicity and efficacy of a COVID-19 vaccine when given in conjunction with a seasonal influenza vaccine. The data obtained showed no adverse effects from the simultaneous administration of NVX-CoV2373 and the influenza vaccine. In other words, the immunogenicity of the influenza vaccine has been preserved; however, scientists observed that a slight reduction occurred in the immunogenicity of the NVX-CoV2373 vaccine. Another striking observation among the 18-65 age group is that the efficacy of the vaccine was preserved in individuals who received both vaccines, compared to those who received only NVX-CoV2373.