Influenza key points

Healthcare providers and local public health departments are instrumental in preventing and controlling the spread of influenza in Massachusetts. Here are some important updates for this year:

2023-2024 Recommendation Highlights

Table of Contents

Influenza Activity During the 2022-2023 Influenza Season

The 2022-23 influenza season in the United States was considered moderately severe with an estimate of at least 31 million symptomatic illnesses, 14 million medical visits, 360,000 hospitalizations, and 21,000 deaths caused by influenza virus infection. The predominant influenza virus throughout the 2022-23 influenza season was influenza A(H3N2); however, as activity declined, A(H1N1)pdm09 and B/Victoria viruses began circulating at higher proportions than A(H3N2) viruses. Most influenza viruses tested were in the same genetic subclade as, and antigenically similar to, the vaccine reference viruses included in the season’s influenza vaccine. All the influenza viruses collected and tested for antiviral resistance by CDC since October 2, 2022, were susceptible to zanamivir, and peramivir and the majority (>99%) were susceptible to oseltamivir and baloxivir.

The 2022-23 season marked a return to influenza activity at levels more similar to those seen prior to the COVID-19 pandemic. The peak percentage of specimens testing positive for influenza (26.3%) as reported to CDC from clinical laboratories nationally was similar to the average peak percentage positive (26.5%) during the five influenza seasons (2015-16 – 2019-20) immediately preceding the COVID-19 pandemic. Similarly, the cumulative rate of influenza-associated hospitalizations as reported in FluSurv-NET this season was similar to hospitalization rates for 4 pre-COVID seasons (2014-15, 2016-17, 2018-19, and 2019-20 seasons) and higher than all but one remaining season (2017-18 season) since the 2010-11 season.

Mortality attributed to influenza also returned to levels more similar to what was seen before the COVID-19 pandemic. As of September 14, 2023, the number of death certificates with influenza listed as an underlying or contributing cause of death during the 2022-23 season (9,697) was above the average number of influenza coded deaths (8,530) during the five seasons preceding the COVID-19 pandemic (2015-16 through 2019-20) and 3 to 10 times higher than the number of influenza coded deaths during the first two years of the COVID-19 pandemic. The number of pediatric deaths reported this season (179) was above the average reported number of deaths each season (147) for the five seasons preceding the COVID-19 pandemic.

Although influenza activity in the United States returned to levels similar to pre-COVID-19 influenza seasons, timing of activity occurred earlier than usual. During the 2022-23 season, activity peaked nationally between late November and early December (depending on the indicator) which is at least three weeks before the earliest recorded seasonal peak going back to the 1997-1998 season and two months before the most common month for peak influenza activity (February). Influenza activity returned to interseasonal levels in February 2023, and no significant second wave of activity was reported.


Prevention and Control of Seasonal Influenza with Vaccines: Recommendations of the Advisory Committee on Immunization Practices — United States, 2023–24 Influenza Season has been published. CDC recommends annual influenza vaccination for everyone 6 months and older who do not have contraindications. 

What’s New for 2023-2024 

  • The composition of the 2023–24 U.S. seasonal influenza vaccines includes an update to the influenza A(H1N1)pdm09 component.
  •  Regarding influenza vaccination of persons with egg allergy, ACIP recommends that all persons aged ≥6 months with egg allergy should receive influenza vaccine. Any influenza vaccine (egg based or nonegg based) that is otherwise appropriate for the recipient’s age and health status can be used. It is no longer recommended that persons who have had an allergic reaction to egg involving symptoms other than urticaria should be vaccinated in an inpatient or outpatient medical setting supervised by a health care provider who is able to recognize and manage severe allergic reactions if an egg-based vaccine is used. Egg allergy alone necessitates no additional safety measures for influenza vaccination beyond those recommended for any recipient of any vaccine, regardless of severity of previous reaction to egg. All vaccines should be administered in settings in which personnel and equipment needed for rapid recognition and treatment of acute hypersensitivity reactions are available.
  • Consistent with prior guidance, everyone 6 months and older should get a flu vaccine, ideally by the end of October. Flu vaccination is especially important for people who are at higher risk of developing serious flu complications, like those with certain chronic health conditions and people 65 years and older.  
  • More information about the 2023-2024 flu season is available at 2023-2024 CDC Flu Vaccination Recommendations Adopted

 For more information on this year’s flu recommendations, see: 

There are some websites that help providers and patients locate vaccines: 

  • Flu vaccine locations  

Find out where you can get a flu vaccine by asking your primary care provider, going to a local pharmacy, or visiting Find your flu vaccine.  

  • COVID-19 vaccine locations 

Search VaccineFinder for a site near you.  

Influenza disease burden

Despite the lower levels of influenza during the pandemic, the overall burden of disease is great. CDC estimates that influenza has resulted in between 9 million and 41 million illnesses, between 140,000 and 710,000 hospitalizations and between 12,000 and 52,000 deaths annually between 2010 and 2020.

Preliminary in-season estimates of influenza burden in the United States for the 2022-23 season are that influenza virus infection resulted in 31 million symptomatic illnesses, 14 million medical visits, 360,000 hospitalizations, and 21,000 deaths.

CDC posts preliminary estimates of the influenza disease burden.  

Every year influenza vaccines are updated to better match circulating viruses.

Your strong recommendation is important!

A health care provider’s strong recommendation is a critical factor affecting whether your patient gets influenza vaccine. Patients listen to providers when providers strongly recommend vaccination. 

  • There are many misconceptions about flu vaccine.  CDC addresses many of these misconceptions and provides a summary of the benefits of vaccination and selected scientific studies that support these benefits. 
  • Flu vaccine is recommended for everyone 6 months of age and older who do not have contraindications. While some flu formulations are not recommended for some patients and some patients should not receive flu vaccine at all, this is uncommon. For more guidance on contraindications and precautions for influenza vaccine, please see Table 3 on page 4 in the  2023-24 Summary of Flu Vaccine Recommendations and pages 16-18 in the 2023-2024 ACIP Influenza Recommendations 

Below are the links to the latest information and data that might inform your conversations with patients in the upcoming months:  

  • Flu vaccine offers the best protection against flu-related illness, hospitalization, and death. Flu vaccine reduces this burden of illness.
  • For the latest information about vaccine effectiveness,
  • Influenza vaccination was found to reduce deaths in children. A study in Pediatrics was the first of its kind to show that influenza vaccination is effective in preventing influenza-associated deaths among children. A 2022 study showed that flu vaccination reduced children’s risk of severe life-threatening influenza by 75%.  And a 2020 study found that during the 2018-2019 flu season, flu vaccination reduced flu-related hospitalization by 41% and flu-related emergency department visits by half among children (aged 6 months to 17 years old).
  • Influenza vaccination may make illness milder. While some people who get vaccinated may develop influenza, vaccination may make their illness milder. A 2017 study in Clinical Infectious Diseases (CID) showed that influenza vaccination reduced deaths, intensive care unit (ICU) admissions, ICU length of stay, and overall duration of hospitalization among hospitalized influenza patients. A 2021 published study found that in a primarily older population, influenza vaccination was associated with a 41% reduction in risk of hospitalized influenza illness. Journal of Infectious Diseases.
  • Influenza vaccination has been found effective in preventing influenza-associated hospitalization during pregnancy.  

For more information on questions and answers related to this flu season, please see the General information about flu page.  

Vaccine supply

MDPH universally provides influenza vaccine, as well as other routinely recommended vaccines, to all children through 18 years of age. MDPH only provides influenza vaccine for uninsured adults seen at public sites. For more information on state-supplied vaccine, please see the Vaccine Management page.  

Nationally, manufacturers have projected they will provide as many as 156-170 million doses of flu vaccine this season. All flu vaccines for the 2023-2024 season will be quadrivalent (four component). Most will be thimerosal-free or thimerosal-reduced vaccine (91%), and about 21% of flu vaccines will be egg-free. Information about the national vaccine supply can be found at CDC’s Seasonal Influenza Vaccine Supply & Distribution website.  

The Immunization Action Coalition (IAC) has a very helpful table of the Influenza Vaccine Products for the 2023-2024 Influenza Season

When to vaccinate

For most persons who need only one dose of influenza vaccine for the season, vaccination should ideally be offered during September and October. However, vaccination should continue throughout the season, as long as influenza viruses are circulating. The duration of the influenza season varies from, year to year and influenza activity might not occur in certain communities until February or March. In New England, flu activity usually lasts until April and May. 

To avoid missed opportunities, providers should continue to offer vaccination during routine health care visits and hospitalizations.

Safe influenza vaccine administration

CDC provides comprehensive vaccine administration resources, including Vaccine Administration eLearn at their Vaccine Administration website

Vaccine information statement

The most recent versions of Vaccine Information Statements (VISs) for Influenza Vaccines (IIV and LAIV4)  for use this season are dated 8-06-21. The latest versions of all the VISs can be found at this site.


2023-2024 Influenza Season – Fall Vaccination Clinics

Centers for Disease Control and Prevention 

Immunization Action Coalition 


  • VaccineFinder Find out where you can get a flu vaccine by visiting

American Academy of Pediatrics 

American College of Physicians 

American Academy of Family Physicians 

American College of Obstetricians and Gynecologists 

Children’s Hospital of Philadelphia 


Contact   for Influenza key points

Date published: February 13, 2024

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