How long vaccines last

These act as training sites for immune cells, teaching them to recognise SARS-CoV-2, indicating a potential for long-lasting protection. Initial studies only evaluated short-term efficacy, however recent research has found strong antibody activity at six months. Variants such as Delta, which are more transmissible and potentially more dangerous, are likely to increase interest in booster programs.

All vaccines show modestly reduced efficacy against Delta , so any decrease in protection over time could be more problematic than with the original SARS-CoV-2 virus, or other variants.

A recent preprint a study yet to undergo peer review found protection against the Delta variant waned within three months with both the Pfizer and AstraZeneca vaccines. This study shows vaccinated people who become infected with Delta still carry high amounts of virus viral load. Third booster doses will be important to reduce these breakthrough infections and subsequent transmission.

Although the UK study looked at infections rather than hospitalisations or deaths, data from around the world continue to show the unvaccinated are making up the vast majority of patients who develop serious illness. Nonetheless, scientists are continuing to investigate how waning immunity could affect protection against the more serious outcomes of COVID Pfizer has reported positive results from trials of a third dose to boost immunity, and the company is seeking formal approval for a booster from the United States Food and Drugs Administration.

It should be noted that the trial occurred prior to Delta becoming the predominant virus variant. Another measure is T cells, which scientists are still studying for their ability to kill virus-infected cells in the context of COVID, and which may also provide important protection.

T cells are more difficult to measure, Iwasaki says. But they may be important—last year, a study in Nature showed that people who were infected with severe acute respiratory syndrome SARS , a different coronavirus outbreak that killed almost people in , maintained T-cell immunity 17 years after they recovered.

Still another way to predict how long protection might last is by looking at natural immunity, says Dr. No one knows for sure whether one vaccine will last longer than another. Meyer says. The two mRNA vaccines use a relatively new technology that delivers a tiny piece of genetic code from the SARS CoV-2 virus into the body to provide instructions for making copies of spike proteins that will stimulate an immune response.

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