Is it worth getting a flu shot after recently recovering from influenza?

Should You Get a Flu Shot After Recently Recovering from Influenza?

Yes, you should still get the flu shot even after recently recovering from influenza, because infection with one strain provides only strain-specific immunity and does not protect against other circulating influenza strains that season. 1

Why Vaccination Remains Important After Infection

Strain-Specific Nature of Influenza Immunity

• Antibody responses to influenza A are primarily strain-specific, meaning immunity to one influenza virus subtype confers limited or no protection against another subtype. 1
• Each flu season typically involves circulation of multiple influenza strains (usually two type A subtypes and one or two type B lineages), so infection with one strain leaves you vulnerable to others. 2
• The strain-specific nature of antibody responses means that immunity from one infection provides limited protection against future infections with antigenically distinct strains. 1

Vaccine Composition vs. Natural Infection

• The influenza vaccine contains antigens from multiple virus strains (three strains in trivalent or four in quadrivalent formulations) representing the influenza viruses likely to circulate during the season. 2
• Your recent infection likely involved only one of these strains, leaving you unprotected against the other strains included in the vaccine. 1
• Influenza viruses undergo continuous antigenic drift through point mutations, creating new variants that can evade existing immunity even within the same subtype. 1

Timing and Safety Considerations

When to Vaccinate After Recovery

• Minor illnesses, with or without fever, are not contraindications to influenza vaccination. 2, 3
• You can receive the flu shot as soon as you have recovered from the acute illness and no longer have moderate-to-severe symptoms. 2, 3
• If you have significant nasal congestion that would impede vaccine delivery, this only matters for the nasal spray vaccine (LAIV), not injectable vaccines. 2, 3

Safety Profile

• The influenza vaccine cannot cause influenza infection because it contains only noninfectious viruses that have been rendered inactive. 1
• The most frequent side effect is soreness at the vaccination site lasting up to 2 days, reported by less than one-third of vaccine recipients. 1
• There is no increased risk or safety concern associated with receiving the vaccine shortly after recovering from influenza. 2

Clinical Benefits of Vaccination

Protection Against Severe Outcomes

• Even if vaccination doesn't prevent all influenza infections, it can be effective in preventing lower respiratory tract involvement or other secondary complications, thereby reducing the risk for hospitalization and death. 2
• During the 2017-18 season, vaccination prevented an estimated 109,000 hospitalizations and 8,000 deaths despite moderate overall vaccine effectiveness. 2
• The vaccine is 50-60% effective in preventing hospitalization and pneumonia and 80% effective in preventing death among high-risk populations like the elderly. 2

Duration of Natural Immunity

• Protection from vaccination typically lasts 6-8 months in healthy non-elderly populations, and natural immunity follows similar patterns. 1
• Immunity declines in the year following vaccination or infection, necessitating annual vaccination even when vaccine strains remain unchanged. 1
• Do not assume that prior influenza infection provides broad, long-lasting protection—the highly mutable nature of influenza means individuals remain susceptible to new variants. 1

Special Populations

High-Risk Individuals

• Vaccination is particularly important for persons at high risk for complications, including those ≥65 years, young children, pregnant persons, and those with chronic medical conditions. 2
• For adults ≥65 years, preferentially receive high-dose inactivated vaccine (HD-IIV4), recombinant vaccine (RIV4), or adjuvanted vaccine (aIIV4). 2

Healthcare Workers and Close Contacts

• Healthcare workers and household members in close contact with high-risk persons should be vaccinated to reduce transmission risk. 2

Common Pitfalls to Avoid

• Don't assume cross-protection: Recent infection with one strain does not mean you're protected against all influenza viruses circulating that season. 1
• Don't delay unnecessarily: As long as you've recovered from acute symptoms, there's no medical reason to wait before getting vaccinated. 2, 3
• Don't skip vaccination in low-effectiveness years: Even when vaccine effectiveness is reduced (as low as 16% in some seasons), vaccination can still prevent serious outcomes like hospitalization and death. 4
• Don't confuse vaccine side effects with infection: Soreness at the injection site or mild systemic symptoms are not influenza infection, as the vaccine cannot cause flu. 1