Focus on Seasonal Influenza 2020-2021

By Allen Lefkovitz

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October 2020

A “twindemic”, “a flu season wrapped in a global pandemic”, and “a perfect storm” – each of these descriptions have been used by health officials to emphasize the importance of the influenza vaccine during the ongoing coronavirus disease 2019 (COVID-19) pandemic. As they have since 2010, the Advisory Committee on Immunization Practices (ACIP) continues to recommend routine annual influenza vaccination for everyone 6 months of age or older who do not have contraindications. Officials from the Centers for Disease Control and Prevention (CDC) describe influenza vaccination as “the most important thing we can do to help protect ourselves, our loved ones and our community from flu, including reducing the risk of serious outcomes that can lead to hospitalization and death.” The 2020-2021 ACIP recommendations provide a few updates and many reminders, but ACIP stresses the importance of influenza vaccination “... to reduce prevalence of illness caused by influenza [that] will reduce symptoms that might be confused with those of COVID-19. 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 U.S. health care system.” Following a high severity 2017-2018 season and a prolonged 2018- 2019 season, the importance of vaccinating for the 2020-2021 influenza season cannot be overstated.

Influenza Vaccines for 2020-2021

The composition of the influenza vaccines for 2020-2021 is described in the table, but represents a change in three of the four strains since last year’s quadrivalent vaccines. This year CDC also recommended different compositions for egg- based versus non-egg-based vaccines, in order to account for different manufacturing processes while still providing the same overall protection.

To see the chart, download the full PDF

CDC has worked with manufacturers to increase vaccine availability for the upcoming season, so while an overall shortage is not anticipated at this time, availability of specific formulations could be limited. Ten influenza vaccines are anticipated to be available for the 2020- 2021 season, and are outlined in the table on page 2. All except for one product (Fluad) will be quadrivalent formulations. This season, two new influenza vaccines include Fluad Quadrivalent, and the Fluzone High-Dose

To see the chart, download the full PDF

Quadrivalent, which was previously only available as a trivalent formulation. An important difference to be aware of with Fluzone High-Dose Quadrivalent is that the volume administered in each injection is 0.7 mL intramuscularly, instead of the 0.5 mL dose used for all other injectable influenza vaccines. 

Timing of Influenza Vaccine Administration

ACIP recommends that “Optimally, vaccination should occur before onset of influenza activity in the community”, and since it can take about 2 weeks to develop the necessary antibodies, they recommend vaccination “by the end of October.” Because of COVID-19, many are suggesting vaccination efforts begin as soon as possible. However, routine vaccination should be deferred for individuals with suspected or confirmed COVID-19, regardless of symptoms until criteria have been met for them to discontinue isolation (e.g., no fever in the past 24 hours, improvement in symptoms; for more details see pandemic-guidance/index.html). CDC continues to encourage that “Vaccination efforts should continue throughout the season because the duration of the influenza season varies, and influenza activity might not occur in certain communities until February or March.”

Allergies and Influenza Vaccination

CDC suggests that if a person reports history of a severe allergy (e.g., anaphylaxis, angioedema) to any known substance contained in a vaccine (e.g., neomycin), an alternative vaccine that does not contain that substance should be considered instead of complete avoidance of vaccination. However, “a previous severe allergic reaction to any influenza vaccine, regardless of the component suspected of being responsible for the reaction, is a contraindication to future receipt of the influenza vaccine.” CDC recommends that prescribers consider the prophylactic use of antiviral medications (e.g., oseltamivir) for individuals who are medically unable to receive influenza vaccination. 

Except for recombinant influenza vaccine [(RIV4) i.e., Flublok Quadrivalent] and cell culture-based inactivated influenza vaccine [(ccIIV4) i.e., Flucelvax Quadrivalent], all influenza vaccines are made by growing viruses in embryonated chicken eggs and may contain small amounts of egg protein. ACIP recommends that anyone with a history of severe allergic reaction to eggs (i.e., more than hives) may receive any recommended and age appropriate influenza vaccine. However, if a vaccine other than Flublok Quadrivalent or Flucelvax Quadrivalent is to be administered to someone who has a more severe reaction to eggs (e.g., respiratory distress, swelling), the vaccine should be administered:

  • in an inpatient or outpatient medical setting (including but not necessarily limited to hospitals, clinics, health departments, and physician offices); and
  • only under the supervision of a healthcare provider who can recognize and manage severe allergic conditions.

As a general precaution, vaccinated individuals (regardless of allergies) should be monitored for 15 minutes after vaccination to watch for allergic reaction and to decrease the risk of injury due to syncope. 

Influenza Vaccines and the Older Adult

Unless otherwise medically contraindicated, being vaccinated is always preferable to not being vaccinated. But ACIP acknowledges that “The effectiveness of influenza vaccination varies depending upon several factors”, including the recipient’s health and age, the type of vaccine received, and the circulating influenza viruses. As they did last year, ACIP continues to note that “early vaccination (i.e., in July and August) is likely to be associated with suboptimal immunity
before the end of the influenza season, particularly among older adults.” This is because vaccine response may be reduced in older adults due to weakening of their immune system and overall frailty. 

Since ACIP does not recommend the practice of revaccination (i.e., providing a booster dose) to anyone properly vaccinated, “active research” to help improve vaccine response and effectiveness for older adults has primarily revolved around three types of vaccines:

  • Fluzone High-Dose Quadrivalent (HD-IIV4)
    • contains four times the amount of antigen compared to SD-IIV4
  • Flublok Quadrivalent (RIV4) – recombinant vaccine that contains three times the antigen
  • compared to SD-IIV4
  • Fluad (aIIV3) and Fluad Quadrivalent (aIIV4) – contain an adjuvant that enhances the body’s
  • response to the vaccine but is the least studied of these options

Influenza Vaccination and Long-Term Care

Nursing Home Compare data currently indicate that 96% of long-stay residents and 82.9% of short- stay residents who “needed” an influenza vaccine received it. ACIP continues to classify all residents of nursing homes and other long-term care facilities (LTCF) as being at “higher risk for influenza-related complications”. In support of CDC recommendations, the Centers for Medicare and Medicaid Services (CMS) states “Facilities should administer the influenza vaccine when it becomes available to the facility.” Within F883 “Influenza and pneumococcal
immunizations”, CMS states that LTCF are expected to have policies and procedures in place that ensure:

  • each resident or their representative receives education about the benefits and potential side
  • effects of the immunization;
  • influenza immunization (without any guidance related to vaccine type) is offered from October 1 through March 31 annually, unless the immunization is medically contraindicated or they have already been immunized;
  • the resident or their representative has the opportunity to refuse immunization; and
  • the resident’s medical record includes, at a minimum, documentation of the aforementioned education and that the resident either received the influenza vaccine or did not receive it due to a medical contraindication or refusal. 

Extra attention must also be given to those who have direct contact with long-term care residents. ACIP states this may include (but not be limited to) “physicians, nurses, nursing assistants, nurse practitioners, physician assistants, therapists, technicians, emergency medical service personnel, dental personnel, pharmacists, laboratory personnel, autopsy personnel, students and trainees, contractual staff, and other persons not directly involved in patient care but who can potentially be exposed to infectious agents (e.g., clerical, dietary, housekeeping, laundry, security, maintenance, administrative, billing, and volunteers).” CDC recognizes that “Influenza vaccination among health care personnel in long-term care settings is especially important because influenza vaccine efficacy is generally lowest among the elderly, who are at increased risk for severe disease”. 

To see the chart, download the full PDF

Unfortunately, the most recent information from the 2018-2019 season continues to indicate that LTCF remain the segment of healthcare with the lowest vaccination rate among healthcare professionals at 67.9% (compared to an overall average of 81.1%). As a result, CDC strongly encourages efforts to improve vaccination coverage in LTCF, especially among staff.

To prepare for the upcoming and unpredictable influenza season, please refer to the summary of the ACIP recommendations and other helpful influenza resources available at:


HealthLine Newsletter - October 2020
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