Antibody levels fell to low or near zero within the first few months of getting the vaccine, unless the person had previously received a smallpox vaccine, scientists reported Saturday at the European Congress of Clinical Microbiology and Infectious Diseases in Barcelona.
The mRNA-1283 vaccine showed a higher immune response—including in seniors—than its currently licensed vaccine, called mRNA-1273.222. Response was higher against Omicron BA.4/BA.5 as well as the original SARS-CoV-2 virus.
The Covid pandemic marked the first time people armed with powerful scientific tools could study how the immune system awakens to and develops defenses against a new threat, in real time, in the global population.
New guidelines suggest certain high-risk groups could benefit from having another dose of a COVID-19 vaccine this spring — and more frequent shots in general — while the broader population could be entering once-a-year territory, much like an annual flu shot.
Medical experts told CBC News that falling behind on the latest shots can come with health risks, particularly for individuals who are older or immunocompromised.