Influenza Vaccination Critical During Pandemic, CDC Says

The Centers for Disease Control and Prevention (CDC) is urging all individuals who are without contraindications to receive the influenza vaccine for the 2020 – 2021 influenza season, saying it is even more important during the COVID-19 pandemic than in normal years.

"Prevention of and reduction in the severity of influenza illness and reduction of outpatient illnesses, hospitalizations, and intensive care unit admissions through influenza vaccination also could alleviate stress on the US health care system," write the authors of recommendations published August 20 in Morbidity and Mortality Weekly Report.

"Influenza vaccination of persons aged ≥6 months to reduce prevalence of illness caused by influenza will reduce symptoms that might be confused with those of COVID-19," they write.

The CDC's Advisory Committee on Immunization Practices (ACIP) recommends routine yearly influenza vaccination for all individuals aged 6 months and older who are without contraindications to the vaccine.

The committee does not recommend any one influenza vaccine product over another for individuals "for whom more than one licensed, recommended, and appropriate product is available," Lisa A. Grohskopf, MD, from the Influenza Division, National Center for Immunization and Respiratory Diseases, CDC, and colleagues explain.

Grohskopf and colleagues note that limited information is available regarding influenza vaccination and COVID-19. Clinicians may consider postponing influenza vaccination of patients with suspected or laboratory-confirmed COVID-19 until they are not acutely ill; however, they should remind patients to return for influenza vaccination after they have recovered.

The ACIP recommendations include updated information regarding newer influenza antiviral agents. Individuals who are receiving influenza antiviral medications "for treatment or chemoprophylaxis" may receive inactivated influenza vaccine (IIV) or recombinant influenza vaccine (RIV4).

However, there are no data on vaccination with LAIV4 in the setting of influenza antiviral use, and antiviral medications could interfere with the LAIV4, inasmuch as it contains live virus, the authors explain.

High-Risk Groups Should Be Given Priority

When influenza vaccines are limited, the authors recommend that the following groups be prioritized for receipt of the vaccine, in no particular order of preference:

Infants and young children aged 6 through 59 months;
Adults aged 50 years and older;
Those with chronic pulmonary disease (including asthma) and cardiovascular disease (excluding isolated hypertension), renal, hepatic, neurologic, hematologic, or metabolic disorders (including diabetes mellitus);
Those who are immunocompromised for any reason, including, but not limited to, patients who are immunocompromised as a result of medications or HIV infection;
Women who are or who expect to be pregnant during the influenza season;
Children and adolescents aged 6 months through 18 years who are receiving aspirin- or salicylate-containing medications who might be vulnerable to developing Reye syndrome associated with influenza;
Individuals living in nursing homes and long-term care facilities;
American Indians/Alaska Natives;
Extremely obese individuals (for adults, those with a body mass index ≥40);
Caregivers of and those who are in contact with individuals at risk, including healthcare personnel and household contacts and caregivers of children younger than 5 years or individuals with medical conditions linked to increased risk for severe complications from influenza.

Vaccine Component Changes

For the 2020 – 2021 influenza season, trivalent and quadrivalent vaccines will update the influenza A(H1N1)pdm09, influenza A(H3N2), and influenza B/Victoria lineage components. Quadrivalent vaccines will also contain a second influenza B virus component from the B/Yamagata lineage, which is the same as that used during the previous influenza season.

For US egg-based influenza vaccines — cell culture–based inactivated vaccine (ccIIV4) and RIV4 — hemagglutinin (HA) will come from an influenza A/Guangdong-Maonan/SWL1536/2019 (H1N1)pdm09-like virus, an influenza A/Hong Kong/2671/2019 (H3N2)-like virus, and an influenza B/Washington/02/2019 (Victoria lineage)-like virus. Quadrivalent egg-based vaccines will also contain an influenza B/Phuket/3073/2013 (Yamagata lineage)-like virus.

For US cell culture–based inactivated (ccIIV4) and RIV4 vaccines, HA will come from an influenza A/Hawaii/70/2019 (H1N1)pdm09-like virus, an influenza A/Hong Kong/45/2019 (H3N2)-like virus, an influenza B/Washington/02/2019 (Victoria lineage)-like virus, and an influenza B/Phuket/3073/2013 (Yamagata lineage)-like virus.

New Vaccines

Two new influenza vaccines have been licensed this season. The US Food and Drug Administration (FDA) approved Fluzone High-Dose Quadrivalent (HD-IIV4) in November 2019 for individuals aged 65 years and older; it will likely replace Fluzone High-Dose (HD-IIV3) trivalent vaccine. The dose volume is higher for the quadrivalent (0.7 mL) formulation than for the trivalent (0.5 mL) vaccine, and both formulations contain four times the amount of HA per vaccine than the standard-dose inactivated influenza vaccines (60 μg per virus, vs 15 μg in standard-dose IIVs).

In addition, the FDA approved Fluad Quadrivalent (aIIV4) in February 2020. It is approved for individuals aged 65 years and older. Both the quadrivalent formulation and the previously licensed trivalent formulation will likely be available for the 2020 – 2021 influenza season. Both formulations contain the adjuvant MF59.

Other Changes

Information on contraindications and precautions regarding the use of LAIV4 will now include "anatomic and functional asplenia; active communication between the cerebrospinal fluid (CSF) and oropharynx, nasopharynx, nose, or ear or any other cranial CSF leak; and cochlear implant."

For persons who have a history of severe allergic reaction to egg, the committee recommends that additional measures be taken, such as supervision of vaccination by a healthcare provider capable of identifying and managing severe allergic reactions, but only for patients who are receiving a vaccine other than ccIIV4 or RIV4.

Additional information about influenza vaccines is available on the CDC's website.

Morb Mortal Wkly Rep. Published online August 20, 2020. Full text

Troy Brown is an award-winning Medscape contributor with a special interest in infectious diseases, women's health, and pediatrics.

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