Complex Vaccination Recommendations From the U.S. CDC

The US Centers for Disease Control and Prevention published an update to the Advisory Committee on Immunization Practices (ACIP) recommendations regarding the use of seasonal influenza vaccines for the 2020-2021 flu season.

This new CDC report, published on August 20, 2020, says this influenza season will coincide with the continued circulation of the SARS-CoV-2 coronavirus associated with the COVID-19 disease pandemic. The extent to which SARS-CoV-2, the novel coronavirus that causes COVID-19, will circulate during the 2020–21 influenza season, ‘is unknown.’

Unfortunately, the common symptoms of COVID-19 can also occur with an influenza illness.

To mitigate this confusion, the CDC suggests everyone over the age of 6-months get a flu shot.

Optimally, vaccination should occur before the onset of influenza activity in the community. However, because the timing of the onset, peak, and decline of influenza activity varies, the ideal time to start vaccinating cannot be predicted each season. 

Moreover, more than 1 outbreak might occur in a given community in a single year. 

In the United States, localized outbreaks that indicate the start of seasonal influenza activity can occur as early as October. However, in 27 (75%) of 36 influenza seasons from 1982–83 through 2017–18, peak influenza activity (which often is close to the midpoint of influenza activity for the season) has not occurred until January or later, says the CDC.

Because SARS-CoV-2 is a novel coronavirus, clinical experience with influenza vaccination of persons with COVID-19 is limited. For those who have acute illness with suspected or laboratory-confirmed COVID-19, clinicians can consider delaying influenza vaccination until they are no longer acutely ill.

If influenza vaccination is delayed, patients should be reminded to return for influenza vaccination once they have recovered from their acute illness.

Furthermore, with various coronavirus vaccine candidates in late-stage studies, there may be added confusion between vaccine efficacy.

The effectiveness of influenza vaccination varies depending on several factors, such as the age and health of the recipient; the type of vaccine administered; the types, subtypes, and lineages of circulating influenza viruses; and the degree of similarity between circulating viruses and those included in the vaccine.

During six previous influenza seasons, the overall estimated vaccine effectiveness was reported to be 38 percent (62% against influenza A[H1N1]pdm09 viruses, 22% against influenza A[H3N2] viruses, and 50% against influenza B viruses).

In recent years, several vaccines containing nonaluminum adjuvants have been licensed for use in the USA for the prevention of various infectious diseases, says the CDC.

These include Shingrix (recombinant zoster subunit vaccine); MF59 (in Fluad and Fluad Quadrivalent); and CpG 1018 (in Heplisav-B, recombinant hepatitis B surface antigen vaccine).

Data are limited regarding co-administration of these vaccines with other adjuvanted or nonadjuvanted vaccines. The immunogenicity and safety of simultaneous or sequential administration of two nonaluminum-adjuvant–containing vaccines has not been evaluated, and the ideal interval between such vaccines, when given sequentially, is not known. 

In the study of Shingrix and IIV4, most reactogenicity symptoms resolved within 4 days. 

Because of the limited data on the safety of simultaneous administration of two or more vaccines containing nonaluminum adjuvants and the availability of nonadjuvanted influenza vaccine options, selection of a nonadjuvanted influenza vaccine may be considered in situations in which influenza vaccine and another vaccine containing a nonaluminum adjuvant are to be administered concomitantly, says the CDC.

And as recommended for all vaccines, vaccines with nonaluminum adjuvants should be administered at separate anatomic sites from other vaccines that are given concomitantly.

These recommendations apply to U.S.-licensed influenza vaccines used within the Food and Drug Administration (FDA)–licensed indications.

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