FAQ: COVID-19 Vaccines

mRNA (messenger RNA) vaccines teach cells how to make a protein that triggers an immune response:

1. The vaccine delivers mRNA instructions for the spike protein of SARS-CoV-2
2. Your cells use these instructions to produce the spike protein (not the virus)
3. The immune system recognizes this protein as foreign and creates antibodies
4. The mRNA degrades within days — it does not enter the cell nucleus or alter DNA

Source: CDC mRNA Vaccines

Effectiveness varies by variant, vaccine, and outcome:

• Initial series: 70-95% effective at preventing symptomatic infection (original strains)
• Severe disease: 90%+ effective at preventing hospitalization and death
• Omicron variants: Reduced transmission prevention but sustained protection against severe outcomes with boosters

Vaccination + prior infection (hybrid immunity) provides the strongest protection.

Sources: CDC Vaccine Effectiveness

Most common side effects (1-3 days):

• Injection site pain, redness, or swelling
• Fatigue, headache, muscle pain
• Chills, fever, nausea

Rare serious events (monitored via VAERS):

• Anaphylaxis: ~2-5 per million doses (treatable)
• Myocarditis/pericarditis: Higher risk in young males, typically mild
• Thrombosis with thrombocytopenia syndrome (J&J): ~3 per million

Source: CDC Safety

Current CDC recommendations (as of 2024):

• Everyone 65+ should receive updated (2023-2024) COVID-19 vaccine
• Immunocompromised individuals: additional doses may be recommended
• Others may receive updated vaccine based on provider guidance

Recommendations evolve as variants and data emerge.

Source: CDC COVID-19 Vaccine Updates

Key findings from research:

• Prior infection provides some protection but varies significantly by individual
• Hybrid immunity (vaccination + infection) provides broadest, strongest protection
• Natural immunity wanes over time; vaccination boosts and extends protection
• Vaccination provides more predictable protection than infection-induced immunity

Both vaccination and prior infection carry risks — vaccination avoids the risks of COVID-19 infection itself.

Source: Nature: Hybrid Immunity