Not medical advice. This site is general information only. In an emergency call your local emergency number. For advice about your own health, speak to a doctor, pharmacist or other qualified health professional.
FAQ
What was the first vaccine?
Edward Jenner developed the first vaccine against smallpox in 1796. He used cowpox virus to protect against smallpox. The word vaccine comes from vacca, Latin for cow.
How do mRNA vaccines work?
mRNA vaccines deliver genetic instructions that teach cells to produce a viral protein. The immune system then produces antibodies against that protein. mRNA vaccines do not contain live virus and cannot cause infection.
Do vaccines cause autism?
No. Multiple large studies involving millions of children worldwide have found no link between vaccines and autism. The 1998 study claiming a link was retracted as fraudulent.
What is herd immunity?
Herd immunity occurs when enough people are immune to a disease that transmission is interrupted. The threshold varies by disease: for highly contagious measles it is often cited at around 95 percent, while less contagious diseases have lower thresholds.
Are vaccine side effects monitored?
Yes. VAERS, the Vaccine Safety Datalink, and other systems continuously monitor vaccine safety. Rare side effects like intussusception after rotavirus vaccine and myocarditis after mRNA COVID vaccine were detected within months.
How are vaccines tested before approval?
Vaccines undergo preclinical studies, Phase 1 safety trials, Phase 2 immunogenicity trials, and Phase 3 efficacy trials involving thousands of participants. The process traditionally takes many years.