Whether you've had the virus or not, COVID-19 vaccination boosts your immune response and offers the best line of protection

Recently the world reached a milestone of one year since COVID-19 vaccines were first authorized by the FDA and other regulatory agencies around the world. Vaccine protection against COVID-19 has proven to be extremely effective, especially against severe disease, hospitalization and death. Having the virus offers some defense against future illness, but protection after infection is less predictable than protection after vaccination. Protection against COVID-19 from both infection and vaccination wanes over time.

Both booster shots and "hybrid immunity" (a combination of vaccination and infection) significantly increase our bodies' defenses against COVID-19. The increase in protection that hybrid immunity and boosters provide is especially important when you factor in virus variants – such as the highly infectious delta variant and the newly discovered omicron variant that is spreading worldwide. People with immunity that comes only from infection are more susceptible to new variants.

In the case of omicron, much remains to be learned. Scientists have already observed that omicron contains more mutations than other variants of concern, including the delta variant. These mutations may make it easier for the virus to pierce through our immunity shields, whether from vaccination or prior infection. In South Africa, where the variant was first identified, early signs indicate that reinfection rates are higher from omicron than from previous strains of the virus.

"Reinfection, especially very early on, is rare," said Diego Hijano, MD, of St. Jude Infectious Diseases. "But as we have new variants and time lapses after having the infection, it can happen. In addition, there is clear benefit to getting vaccinated, especially as we have new variants emerging in different parts of the world."

Immunity conveyed from vaccination or infection is critical to protecting yourself against severe illness from COVID-19. However, vaccination – including a booster shot – is the most reliable way to ensure protection. When someone recovers from COVID-19, hybrid immunity with all recommended doses of vaccine provides even broader cross-protection against emerging variants.

Both clinical trials and real-world evidence from more than 8.4 billion vaccine doses given worldwide show that side effects from vaccination are generally mild and disappear within two to three days. Severe side effects such as allergic reaction, myocarditis and blood clots are extremely rare.

The outcomes of the disease itself are less easy to predict. Pre-existing conditions such as high blood pressure, diabetes and obesity can complicate the course of COVID-19. When it comes to heart inflammation, research has shown that the risk of myocarditis in people with COVID-19 was 6 – 34 times higher compared to people who received an mRNA vaccine.