CDC Says COVID, Flu Vaccines Can Be Co-Administered

Michael Vlessides

September 16, 2021

When the Centers for Disease Control and Prevention (CDC) released its latest round of recommendations regarding seasonal influenza vaccines, the document contained one notable update: flu vaccines and COVID-19 vaccines can now be given simultaneously.

This change stands in marked contrast to previous recommendations, in which the CDC said that other vaccinations should not be administered within a 2-week window before or after receiving the COVID-19 vaccine.

"We believe flu vaccination is very important in the context of ongoing COVID-19 activity," said Lisa A. Grohskopf, MD, MPH, medical officer, Influenza Division, CDC, in an interview with Medscape Medical News. "First, as COVID-19 cases continue to increase, our healthcare system is increasingly burdened by caring for COVID-19 patients. While flu activity has been unusually low since March of 2020, we are seeing the return of other common respiratory viruses, so we anticipate that we will experience an annual epidemic of flu this season as we do during most winters.

"Substantial flu activity occurring at the same time as COVID-19 activity could overwhelm our healthcare systems," she added.

The update was published online on August 27 in Morbidity and Mortality Weekly Report.

Universal Recommendations Unchanged

Grohskopf explained that the current recommendations ― the product of regular meetings of the Advisory Committee on Immunization Practices' (ACIP's) Influenza Working Group — are intended to guide clinicians in the use of influenza vaccines for the upcoming flu season, from late fall through early spring. Not surprisingly, they recommend routine annual influenza vaccination for all people who are at least 6 months of age and who do not have contraindications.

Following such precautions will not only reduce the prevalence of illness caused by influenza but will also reduce symptoms that might be confused with those of COVID-19, the authors say. In addition, preventing flu and mitigating the severity of its symptoms will likely result in a reduction of outpatient visits, hospitalizations, and intensive care unit admissions, which in turn may alleviate stresses on the healthcare system caused by COVID-19.

"ACIP and CDC's universal flu vaccine recommendation has not changed," Grohskopf noted. "Everyone 6 months of age and older should get a flu vaccine every season, with rare exception. There are some groups of people who are at higher risk of developing severe flu complications, and vaccination is especially important for them. This includes adults 65 years and older, people with certain chronic health conditions (for example, asthma, diabetes, heart disease), pregnant people, and children younger than 5 years old."

Several Updates

In addition to the timing of COVID-19 vaccinations, the recommendations have other notable updates. First, the composition of flu vaccines has been updated such that all vaccines are now quadrivalent, designed to protect against four flu viruses. Additionally, licensure for the Flucelvax Quadrivalent flu vaccine has changed: the approved age indication for the cell culture–based inactivated vaccine has been increased from age 4 years or older to age 2 years or older.

The agency also changed the recommended timing of flu vaccination for some groups of people, including pregnant women in the third trimester, nonpregnant adults, and children who need two doses (ie, those aged 6 months to 8 years who have never received influenza vaccine or who have not previously received a lifetime total of at least two doses). The latest recommendations update guidance regarding contraindications and precautions for the use of the Flucevax Quadrivalent and Flublok Quadrivalent vaccines.

Co-Administration the Focus

The new recommendation regarding co-administration of COVID-19 and flu vaccines dominated the update. Although Grohskopf admitted that there is a paucity of data regarding the safety of co-administration, experience with other vaccine combinations has demonstrated that immune response and potential side effects are generally similar when given alone or with other vaccines.

"Based on this prior experience, we do not anticipate any unusual or unexpected safety problems with giving COVID-19 vaccines and flu vaccines at the same time," she commented.

Americans are now free to get both vaccines at the same time, and Grohskopf was quick to point out that persons should not delay in receiving either vaccine.

"Ideally," she noted, "people should get their flu vaccines by the end of October. If COVID-19 booster shots are approved by FDA and recommended by ACIP, some Americans will not be eligible for their third dose of COVID-19 vaccine until later. People should go ahead and get their flu shot and then schedule their COVID-19 vaccine at the proper time."

Consistent with the CDC recommendations, Andrew Noymer, PhD, did not see any problems with co-administration of the COVID-19 and flu vaccines. "The seasonal flu shot is very well tolerated (has low rates of serious adverse events), as is the COVID shot," commented Noymer, of the Department of Population Health and Disease Prevention at the University of California, Irvine. He was not involved in preparing the CDC recommendations.

In an interview with Medscape Medical News, Noymer commented, "People often wonder, can the body handle two vaccines simultaneously? The answer is yes, and we do this all the time. The MMR vaccine given to children is, in fact, a cocktail of three vaccines, and the MMRV is a cocktail of four. So I'm not concerned by dual administration of influenza and COVID vaccines.

"In some Platonic-ideal sense, it would be better to do the vaccines 2 weeks apart, because then one can disentangle adverse effects," Noymer added. "But these are rare enough at this point that it doesn't concern me. The reason for the recommendation of both at once is attrition: some people who intend to come back for their second shot wind up just skipping it. Thus, do them both at once."

Grohskopf and Noymer have disclosed no relevant financial relationships.

MMWR Morb Mortal Wkly Rep. Published online August 27, 2021. Full text

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