Is this due to the pandemic? Yes and no. In Austria, we don’t see major differences in immunity rates between children born before or during the pandemic—though it might still be too early to say for sure.

What about infants? They're partly protected by maternal antibodies after their birth—but for how long? This matters, since early vaccination can be less effective. We found that almost none of the infants older than 6 months were protected against measles!

While some individuals missed their vaccination, others may have 'lost' their immunity over time—since we know antibody levels can wane. Could that apply to measles too? To some extent, yes: antibody levels drop in the first years after vaccination, but then stabilize—classic exponential kinetics.

We analyzed measles antibody levels in >50,000 individuals born 1922-2021. Almost everyone born before the 70s was immune — likely the hard way: through survival of measles infection (there was no vaccination yet!). However, we found large immunity gaps (yellow) in those born in the last 3 decades!