As a measles outbreak sweeps through Texas, officially sickening 124 people, mostly unvaccinated children, and hospitalizing 18, anti-vaccine groups are pushing a familiar and false theory: The highly contagious virus is being caused by the vaccine itself.

Angela Solis, a pharmacist at Martin's Wellness and Compounding Pharmacies, said measles is the most contagious respiratory illness. She said interest in the MMR vaccine has increased at the pharmacies since the Texas measles outbreak began.