New booster on horizon as COVID-19 numbers tick up

COVID-19 vaccine

Dear Doctors: I would like to know about the new COVID-19 variant called Eris. Will there be a new booster for it? Also, I read that you'll get better immune response if you get all of your COVID shots in the same arm each time. Is this true?

Dear Reader: From the earliest days of the pandemic, health authorities have kept a watchful eye on the emergence of variants of the coronavirus that causes COVID-19. More specifically, they have tracked what are known as variants of interest. These are mutated forms of the original coronavirus that, due to small changes to the genetic code, become more successful at breaking into and infecting host cells.

Among the newest of these is a variant called EG.5, which has come to be known as Eris. It is now the dominant variant in many parts of the world, including the United States. The Centers for Disease Control and Prevention reports that, as of Aug. 21, Eris made up close to 21% of all new COVID-19 infections in the U.S. That's a marked increase over the previous month. However, in terms of symptoms and severity of disease, Eris does not appear to be significantly different from previous variants.

Eris, along with a handful of other variants that are under close scrutiny at this time, is a descendant of the XBB strain of the coronavirus. That strain is the target of the newest generation of coronavirus booster shots. The new coronavirus booster, which still needs regulatory approval from the FDA, is expected to become available sometime this fall. To simplify what has often been a confusing process, the U.S. is shifting to an annual model for COVID-19 boosters for all age groups.

As for your question about which arm to choose for your coronavirus vaccine, new research suggests the decision may play a role in immune response. A recent study found that immune response may indeed be stronger when the COVID-19 vaccine goes into the same arm each time.

Researchers arrived at this conclusion by analyzing data from 303 individuals receiving the original two-dose coronavirus vaccine series. Those who got both shots in the same arm had levels of T cells that were 75% higher than those who switched arms for the second shot. T cells, which are a type of white blood cell, play a crucial role in immune response. Sometimes known as “killer T cells,” they roam throughout the body and attack suspected pathogens.

The researchers suspect the link between vaccine location and higher T cell numbers is due to the proximity of the armpit. T cells are present in lymph nodes, including those located in the armpits. When the immune cells in those lymph nodes are repeatedly stimulated by the vaccine, this could lead to a more robust immunological response. Proving whether this is actually the case will require a larger and longer study. But in the meantime, there is no harm in picking one arm in which to receive all of your COVID vaccines.

(Send your questions to [email protected], or write: Ask the Doctors, c/o UCLA Health Sciences Media Relations, 10960 Wilshire Blvd., Suite 1955, Los Angeles, CA, 90024. Owing to the volume of mail, personal replies cannot be provided.)

Take the Next Step

Visit UCLA Health's Coronavirus page to learn more.