CDC report underlines protection provided by COVID-19 boosters

The Centers for Disease Control and Prevention (CDC) doubled down on its recommendation that everyone receive COVID-19 booster shots after a study they published last week confirmed the effectiveness of boosters in preventing emergency department visits and hospitalization, even from the Omicron variant.

In the period after Omicron became the predominant virus, vaccination followed by a booster shot provided 91% effectiveness against hospitalization and 87% protection against emergency department/urgent care (ED/US) for two months, said a study published by the CDC using VISION-COVID Network records. After four months, protection dropped but was still at 78% effectiveness against hospitalization and 66% against an ED/US visit, the report said.

Along with showing the need for a booster, the study may suggest the necessity of further vaccines in the coming months, CDC said: “The finding that protection conferred by mRNA vaccines waned in the months after receipt of a third vaccine dose reinforces the importance of further consideration of additional doses to sustain or improve protection against COVID-19–associated ED/UC encounters and COVID-19 hospitalizations.”

The importance of T cells

Other studies that similarly find protection against Omicron from vaccination suggest that much of the protection comes from T cells, which last longer than antibodies and have been found to be induced by boosters.

“Cellular immune responses, particularly CD8+ T cell responses, likely contribute to protection against severe SARS-CoV-2 disease,” according to a report in Nature last month. “ These data provide immunologic context for the observation that current vaccines still show robust protection against severe disease with the SARS-CoV-2 Omicron variant despite the substantially reduced neutralizing antibody responses.”

Another study published in Nature last month showed that T cells are effective in fighting the Omicron variant. “The magnitude of Omicron cross-reactive T cells was similar to Beta and Delta variants, despite Omicron harboring considerably more mutations,” said the report.

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