Immune responses to cholera following natural infection: a review

We analyzed the estimated duration of immunity following cholera infection from available published studies. We searched Pubmed and Web of Science for studies of the long-term immunity following cholera infection. We identified 22 eligible studies and categorized them as either observational, challenge, or serological.

We found strong evidence of protection at three years after infection in observational and challenge studies. However, serological studies show that elevated humoral markers of potential correlates of protection returned to baseline within one year. Although with small sample sizes, three studies found that most participants with a subclinical infection from an initial challenge with cholera had a symptomatic infection when rechallenged with a homologous biotype, suggesting that a subclinical cholera infection may confer lower protection than a clinical one.

This review underscores the need to elucidate potential differences in the protection provided by clinical and subclinical cholera infections. Further, more studies are warranted to bridge the gap between the correlates of protection and cholera immunity. Understanding the duration of natural immunity to cholera can help guide control strategies and policy. 

The duration of natural immunity following a cholera infection is unknown. Studies using different methodologies have estimated this duration, obtaining very different asnwers depending on the methodology used (ranging from a few months to several years). Here, we reviewed all published studies and compared their estimated durations. We found three smaller studies that concluded that duration of immunity following an asymptomatic cholera infection is much shorter than immunity following a symptomatic infection.

Understanding the natural history of cholera infection, particularly the mechanisms responsible for long-term protection, are key to prevention, outbreak response, and cholera control. Our results point to the need to further investigate the duration of immunity based on the presentation of symptoms.