26 octubre, 2021

Does infection with or vaccination against SARS-CoV-2 lead to lasting immunity?

Many nations are pursuing the rollout of SARS-CoV-2 vaccines as an exit strategy from unprecedented COVID-19-related restrictions. However, the success of this strategy relies critically on the duration of protective immunity resulting from both natural infection and vaccination. SARS-CoV-2 infection elicits an adaptive immune response against a large breadth of viral epitopes, although the duration of the response varies with age and disease severity. Current evidence from case studies and large observational studies suggests that, consistent with research on other common respiratory viruses, a protective immunological response lasts for approximately 5–12 months from primary infection, with reinfection being more likely given an insufficiently robust primary humoral response. Markers of humoral and cell-mediated immune memory can persist over many months, and might help to mitigate against severe disease upon reinfection. Emerging data, including evidence of breakthrough infections, suggest that vaccine effectiveness might be reduced significantly against emerging variants of concern, and hence secondary vaccines will need to be developed to maintain population-level protective immunity. Nonetheless, other interventions will also be required, with further outbreaks likely to occur due to antigenic drift, selective pressures for novel variants, and global population mobility.

Since its emergence in December 2019, SARS-CoV-2 has continued to cause a considerable burden of acute and chronic disease, placing immense pressure on health systems worldwide. To break chains of transmission and slow the surge in morbidity and mortality associated with the pandemic, governments have employed a range of non-pharmaceutical interventions, including social distancing, mask wearing, testing, contact tracing, travel restrictions, and quarantining. However, the cost of these measures has been a social and economic toll unparalleled in scope, and their rollout for many populations worldwide, provide much hope compared with the worrying public health outlook of 2020. Nonetheless, emerging data on novel genetic variants of SARS-CoV-2, together with evidence of potential reinfections,

Improvements in testing capacity, alongside news of the efficacy of novel vaccines

threaten the notion of immune protection following a primary infection and—of equal, if not more, concern—after vaccination. If the durability of immunity is hindered by changes in the genetic architecture of circulating SARS-CoV-2 strains, this would have key implications for relaxing the stringency of non-pharmaceutical interventions.

To understand the extent of this potential threat, in this Personal View we evaluate research on common respiratory viruses and previous pandemic human coronaviruses, and draw on the large body of emerging immunological data on SARS-CoV-2 infection. We focus on the developing knowledge of cellular and humoral immunity to SARS-CoV-2, in response to both natural infection and vaccination, and present our views on what the available evidence means in terms of the longevity of protective immunity. We discuss areas of concern regarding the emergence of novel variants of SARS-CoV-2 and the growing evidence of human reinfection, and identify priorities for research to address current gaps in understanding.

Créditos: Comité científico Covid

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