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What do we know about immunity before and after Omicron infections?


by Health Desk
Published on January 7, 2022

What our experts say

Whether through vaccination or prior infection, the human immune system can become stronger with repeated exposure to a pathogen and has the ability to remember familiar infections. This happens through what are known as “B cells” of the immune system. These cells can recall previous infections and generate antibodies in response to the new infection. Importantly, this response is not guaranteed. The immunity resulting from both vaccination and infection changes over time, and can change based on which variant causes the infection, how long the virus remains in someone’s body, their age, the vaccine they received and their general health.

Very early, initial research results from South Africa suggest that antibodies from an Omicron infection can be protective against the Delta variant, but this has so far been studied in only 13 patients. Far more research is needed on a larger number of patients before the association can be confirmed.

Additionally, researchers found that individuals who recovered from COVID-19 before getting their vaccines may be more resistant to Omicron’s mutations. This suggests a chance for protection against Omicron, and more research is needed before we can make conclusions about how Omicron will behave.

Experts from the U.S. Centers for Disease Control and Prevention report that even people with antibodies from vaccines can spread the Omicron variant to others.

Despite reports suggesting that it causes milder disease, we should continue to take the same recommended protective measures through social distancing, and vaccination when eligible. This remains the main tool in reducing hospitalizations and transmission in communities to individuals who are more vulnerable and at a greater risk, especially in the case of this highly infectious variant.

Context and background

There are multiple reports of the Omicron variant causing milder disease than other COVID-19 variants. Data on this topic is new and in its early stages. Omicron may be reported as mild because the disease itself is mild, but the age and vaccination status of a country’s population may also be contributing to this outcome. Such questions should reveal themselves with more research. Now that Omicron has spread to more than 20 countries, researchers are working to gather more global data to test these initial assumptions about the variant's severity.

There is also ongoing research to examine the occurrence of breakthrough infections from the Omicron variant. In the past, the Beta variant showed evidence of evading the immune system, and vaccine clinical trials showed little protection against the virus. However, real-world analysis showed that vaccination was more than 80% protective against hospitalization.

Several scientists are now observing patterns that are inline with the South African reports about Omicron changing the prevalence of the Delta variant. As the Omicron cases rose in both Connecticut and London, scientists from Yale School of Public Health and London School of Hygiene and Tropical Medicine reported a decline in cases caused by the Delta variant.

Some experts theorize that this could be a pandemic turning point, where the virus becomes similar to a seasonal threat like influenza. This could be the potential herd immunity that scientists are waiting for— but herd immunity, in reality, would not mean that the virus will disappear. It will likely continue to infect some people as well as animals. Time and additional data and research will uncover how things will develop.

Used with Permission from Health Desk, a public health hub that explains emerging COVID-19 science.

This article was written and edited by the Tayo editorial desk and has been reviewed by an independent panel of subject matter experts.

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