Vaccine FAQ

Vaccines work by training your immune system to recognize and fight specific pathogens (like viruses or bacteria). They contain weakened or inactivated parts of the germ, or genetic instructions for your body to build protective proteins.

When you receive a vaccine, your immune system creates antibodies — specialized proteins that identify and neutralize the real pathogen if you're ever exposed to it. This is called adaptive immunity.

Sources: CDC, WHO

Vaccines undergo rigorous testing for safety and effectiveness before being approved. In the U.S., the FDA requires extensive clinical trials across multiple phases before licensing.

After approval, safety monitoring continues through systems like VAERS (Vaccine Adverse Event Reporting System) and V-safe, which track potential adverse events in real-time.

Sources: FDA Vaccine Safety, CDC Safety Monitoring

Vaccine ingredients vary by type but typically include:

• Antigen: Weakened or inactivated pathogen, or genetic material
• Adjuvants: Compounds like aluminum salts that enhance immune response
• Stabilizers: Sugars or proteins that maintain effectiveness during storage
• Preservatives: Thimerosal (in some multi-dose vials) — all current routine childhood vaccines are thimerosal-free

Sources: CDC Vaccine Ingredients

The CDC's Recommended Immunization Schedule for children from birth to 18 years includes vaccines at specific ages to provide protection when children are most vulnerable. Key milestones include:

• Birth: HepB
• 2 months: DTaP, Hib, IPV, PCV13, Rotavirus
• 12-15 months: MMR, Varicella, HepA
• 11-12 years: Tdap, HPV, Meningococcal

Sources: CDC Immunization Schedules

Most side effects are mild and temporary, indicating the immune system is responding:

• Soreness, redness, or swelling at injection site
• Low-grade fever
• Fatigue or headache
• Muscle or joint aches

Serious adverse events are rare. The benefits of vaccination far outweigh the risks for most people.

Sources: CDC Side Effects

Yes. Children regularly receive multiple vaccines during a single visit. Research shows the immune system can handle thousands of antigens simultaneously. Combination vaccines reduce office visits while maintaining protection.

Studies have not found increased side effects when multiple vaccines are given together compared to giving them separately.

Sources: CDC Multiple Vaccines

Herd immunity (or community immunity) occurs when a sufficient percentage of a population is vaccinated, making it difficult for a disease to spread. This protects those who cannot be vaccinated due to medical conditions or allergies.

The threshold varies by disease — measles requires about 95% vaccination rate, while polio needs around 80-86%.

Sources: WHO Herd Immunity

No. Extensive scientific research has found no link between vaccines and autism. The original 1998 study that suggested a connection was fraudulent and has been retracted. Subsequent studies involving millions of children have consistently found no association.

The CDC, WHO, and major medical organizations worldwide confirm vaccines do not cause autism.

Sources: CDC Autism & Vaccines, Peer-reviewed research