Researchers studying how we respond to vaccines have discovered a molecular signature that could help identify people who have a greater risk of suffering temporary but adverse reactions to immunizations. The findings are published in Nature Immunology this week.
The so-called swine flu is caused by H1N1, the influenza virus that circulated during the outbreak of 2009. It was the first major H1N1 outbreak in several decades, and that means people over 40 might still harbor swine flu-specific memory cells that could be reactivated.
To compare their responses to flu vaccines with those that aren’t heavily influenced by the recall responses of the immune system, Adrian Hayday of King's College London and colleagues tracked 178 healthy people who were immunized with the Pandemrix H1N1 vaccine for swine flu between March 2010 and August 2011. This shot in particular contained an additional compound (called an adjuvant) that’s designed to bolster helpful immune responses. Blood samples were taken before and after the vaccine was administered, and the volunteers self-reported the intensity of various “wellness” parameters including fever, muscle and joint aches, dizziness, diarrhea, swollen glands, and sleeplessness.
Within 24 hours, all of the participants had mounted immune responses. Compared to their pre-vaccination state, they showed major changes in the frequencies of white blood cells circulating in the blood, as well as changes in the genes that these cells express. Additionally, the team found significant differences in this early immune response between volunteers younger than 35 and volunteers 35 or older.
Furthermore, in the 20 percent of participants who reported (temporary) side effects of the vaccine, the team detected a pre-vaccination molecular signature that’s correlated to increased frequencies of immature B cells in the blood. White blood cells called B cells produce antibodies, and transitional B cells (the ones identified in this study) have previously been linked with autoimmune diseases, specifically those that impact joints or connective tissues.
Auto-antibodies, the team found, were present in the blood samples from these (otherwise healthy) people before they got their shot – suggesting that some pre-existing condition factored into the adverse events they experienced as a result.