Medical Health Cluster

1 febrero, 2024

COVID-19 Vaccine Effectiveness

Updated COVID-19 vaccine boosts waning immunity

The virus that causes COVID-19 is always changing, and protection from infection or COVID-19 vaccination declines over time. Receiving an updated 2023-2024 COVID-19 vaccine can restore and provide enhanced protection against the variants currently responsible for most infections and hospitalizations in the United States. New data from CDC show that the updated COVID-19 vaccines were effective against COVID-19 during September 2023 – January 2024, including against variants from the XBB lineage, which is included in the updated vaccine, and JN.1, a new variant that has become dominant in recent weeks.

The virus that causes COVID-19 will continue to evolve

For viruses to survive they must continually make copies of themselves and infect new cells. Like other viruses, SARS-CoV-2, the virus that causes COVID-19, will continue to evolve because it makes errors, or mutations, when it is creating copies. Some mutations help the virus survive better or spread more easily, leading to different variants over time. During the analysis period, many different variants were infecting people.

Updated COVID-19 vaccine protects against many variants

CDC data show that vaccination offered significant protection. People who received the updated COVID-19 vaccine were 54% less likely to get COVID-19 during the four-month period from mid-September to January. The vaccine provided similar levels of protection against XBB lineage variants and the JN.1 variant.

To estimate vaccine effectiveness of the updated COVID-19 vaccine, CDC analyzed data from the Increasing Community Access to Testing (ICATT) COVID-19 pharmacy testing program. The protection provided by the updated vaccine was compared to not receiving an updated vaccine, regardless of a person’s infection history or the number of previous COVID-19 vaccines they received. That means these estimates reflect the additional protection provided by getting an updated COVID-19 vaccine dose above protection that people have from any previous vaccination, infection, or both.

Since protection from prior infections and vaccinations declines over time, stay up to date on vaccines

The updated COVID-19 vaccines have been available since mid-September, so these estimates only include data from the 4 months since the updated vaccine became available. Protection against COVID-19 from earlier versions of the COVID-19 vaccine decreased over several months after vaccination. Based on that, we expect that protection from the updated vaccine will also decline over time. The same is true for the protection derived from infection.

However, most people who are vaccinated and those who had COVID-19 will have some protection from future severe COVID-19. Although the amount and duration of protection from vaccination or infection can vary from person to person, CDC data have demonstrated that original COVID-19 vaccines can help protect against being put on a ventilator and/or death for up to 2 years and bivalent COVID-19 vaccines also provide sustained protection against critical illness and death. Even with this sustained protection it is important that you get your updated COVID-19 vaccine since it can provide additional protection. Additional vaccine effectiveness data against emergency department/urgent care visits and hospitalizations will be shared as they become available.

CDC recommends everyone 6 months or older get an updated COVID-19 vaccine. Vaccination remains the best protection against COVID-19-related hospitalization and death. Vaccination also reduces your chance of suffering the effects of Long COVID, which can develop during or following acute infection and last for an extended duration.

Get vaccinated today

It is not too late to get vaccinated if you haven’t received the updated COVID-19 vaccine.  If more Americans are protected against COVID-19, we will see fewer hospitalizations and deaths. Lives can be saved.

Vaccination is especially important for people at higher risk of severe illness from respiratory diseases, including young children, older adults, people with underlying medical conditions, and pregnant people. People who are moderately or severely immunocompromised may receive one or more additional doses of an updated COVID-19 vaccine.

How to get the vaccines

CDC programs such as the Bridge Access Program, Vaccines for Children, and Partnering for Vaccine Equity are helping people get vaccinated to protect themselves during respiratory virus season.

If you have insurance, these vaccines should be free to you in most cases. Adults without health insurance or adults whose insurance doesn’t cover all COVID-19 vaccine costs can get an updated COVID-19 vaccine for free through the Bridge Access Program. Most children can get recommended vaccines for free through their family’s insurance or the Vaccines for Children (VFC) program.

There’s still time to get vaccinated. Talk with your trusted healthcare provider about which vaccines you and your loved ones need to stay healthy.

Vaccines are available at various locations. Depending on your situation, you may get a vaccine at:

  • Your healthcare provider’s office
  • Your local pharmacy
  • Other locations, such as public health clinics, Federally Qualified Health Centers (FQHC), and Rural Health Clinics (RHC).

For help finding COVID-19 vaccines, visit


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