Every fall the flu vaccine in your refrigerator is a new product, even when the box looks the same as last year's. This article explains why the vaccine is updated every season, when it expires, and what the change means for billing: which codes stay the same and which ones don't.
Why there is a new vaccine every year
There are two reasons:
- The virus changes. Influenza viruses constantly pick up small changes in their surface proteins, a process called antigenic drift. After enough changes, the antibodies from last year's vaccine no longer recognize the virus well.
- Protection fades. Immunity from a flu shot declines over the months after vaccination, so last year's dose doesn't carry a patient through the next season.
So each year the vaccine is reformulated to match the viruses expected to circulate. In the United States, FDA's vaccine advisory committee (VRBPAC) reviews global surveillance data every spring and recommends which strains the next season's vaccines should contain. Manufacturers then produce the new formula over the summer.
What changed for 2026-2027
VRBPAC met on March 12, 2026. U.S. flu vaccines remain trivalent: two influenza A viruses (H1N1 and H3N2) and one influenza B virus (Victoria lineage). According to CDC, all three components were updated compared with the 2025-2026 vaccines, including a change to protect against the H3N2 subclade K virus that spread widely last season.
Does flu vaccine expire?
Yes. Injectable flu vaccine has a standard expiration date of June 30 at the end of the season it was made for: a 2026-2027 dose is good through June 30, 2027. The date has as much to do with the yearly formula change as with shelf life. Manufacturers test potency through the season, and FDA does not recommend using any vaccine past its labeled expiration date.
- Always check the expiration date on the label. Some products expire earlier than June 30.
- Last season's leftover doses should not be given, even if the strains look similar.
- CDC advises that anyone who received an expired flu vaccine should be revaccinated with the current season's vaccine.
Many state immunization programs ask providers to report expired doses as waste after June 30. Ask your distributor or the manufacturer whether unused doses can be returned for credit.
What changes for billing each season
| Item | Each new season |
|---|---|
| CPT vaccine code | Usually the same. The code describes the type of vaccine, not the season. A preservative-free 0.5 mL trivalent shot, for example, is 90656 this season and last. |
| NDC | New. Each season's product gets new NDCs, and last season's are retired. |
| Medicare payment | New allowances, effective for dates of service August 1 through July 31. |
| Expiration | June 30 at the end of the season for injectable vaccine. |
NDCs. Because every season's vaccine is a new product, manufacturers list it under new NDCs. For example, this season's Fluzone Trivalent preservative-free syringe carton is 49281-0426-50. Payers that require an NDC on vaccine claims will reject last season's code. Update the NDCs in your EHR inventory and billing system when the new stock arrives. Our article on NDC formats explains the carton and syringe NDCs and how to convert them to 11 digits.
Medicare pricing. Medicare Part B pays seasonal flu vaccines at 95 percent of the average wholesale price. CMS publishes new payment allowances every year on its Seasonal Influenza Vaccines Pricing page, effective for dates of service August 1 through July 31. For 2026-2027, that is August 1, 2026 through July 31, 2027 (Change Request 14542). Our 2026-2027 flu and COVID-19 vaccine prices page lists this season's codes and payment amounts.
Administration. For Medicare, the flu shot is reported with the vaccine code plus G0008 for the administration. Medicaid and commercial plans may use different administration codes, so check each payer.
The vaccine code usually stays the same, but the NDC and the price change every season. Update both before the first flu claim of the season.
Common flu vaccine billing problems
- Last season's NDC still saved in the EHR or billing system
- Carton NDC sent to a payer that wants the syringe NDC, or the other way around
- Expired vaccine given after June 30, which means the patient needs a new dose
- Charges or fee schedules not updated for the new season's prices
- Administration code that doesn't match the payer (G0008 for Medicare)
Sources
- CDC: 2026-2027 flu season
- FDA: Influenza vaccine composition for the 2026-2027 U.S. season
- CDC MMWR: Administration of expired injectable influenza vaccines
- CMS Transmittal 13859, Change Request 14542: Influenza vaccine payment allowances, 2026-2027 season
- CMS: Vaccine pricing
- CDC: Vaccine code set release notes, July 31, 2026 (new and retired flu NDCs)
If flu vaccine claims are coming back denied this season, our billing team can review them with you.