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What’s the risk of reinfection with a variant?

Question: Building from yesterday’s question, given the rise of more transmissible variants, if I had COVID earlier in 2020, what’s the risk of reinfection with a variant?

Answer: This is another area we’re still learning about.  Individual-level risk varies dramatically based on a range of factors– including vaccination status, degree of exposure, strength of immune response, etc– so I can’t speak to your individual risk.  Instead, I’ll focus on describing what the limited data currently tell us about population-level risk of reinfection.  To keep the post manageable, I’ll also limit descriptions to three variants of concern more frequent in the US:: 

  • Alpha variant is unlikely to increase the risk of reinfection (B.1.1.7, originally detected in the UK). Last month, Lancet published a study examining the association between regional levels of infections with Alpha variant and reported symptoms, disease course, rates of reinfection, and transmissibility. Study authors found that the frequency of reinfection with the Alpha variant was not meaningfully different from the frequency of reinfection with the pre-existing variants, concluding that “B.1.1.7 does not substantially alter the risk of reinfection.”
  • Delta variant might not increase the risk of reinfection (B.1.617 .2, originally detected in India).  We have evidence that neutralizing antibodies from individuals who had previously been infected “neutralized B.1.617 about 50% less effectively than previously circulating strains,” as reported in Nature.  This evidence does not bode well for the risk of reinfection, however, it’s also not enough evidence to make assumptions about increased risk of reinfection.  In more positive news, data released last week from the UK’s SIREN study indicate that the rate of reinfection with the Delta variant is no higher than pre-existing variants. 
  • Gamma variant has been associated with increased risk of reinfection (P.1, originally detected in Brazil).  Study results released last month of blood donors in Manaus, Brazil, found that the risk of reinfection with Gamma variant was higher than anticipated– 1 in 6 individuals previously infected were reinfected with Gamma. As described in this easy-to-read BMJ report on the study, these results confirm “that P.1 is better at evading antibodies in those infected with an older variant, as has been suggested in laboratory studies.”