Another group registers The New England Journal of Medicine earlier this month detailed the pathway of the virus in a 45-year-old man with an autoimmune disease for which he was receiving immunosuppressants. In this case, they found that there was an “accelerated” evolution of the virus in the individual, and that many of the mutations were in the spike protein. Most immunocompromised people clear SARS-CoV-2 infections without major complications, they wrote, but “this case highlights the potential for sustained infection and accelerated viral evolution associated with an immunocompromised state.”
The same phenomenon has been seen in other conditions where the immune system is compromised. HIV attacks immune function, allowing it to evolve at an amazingly fast rate, making it even more difficult for the body to produce antibodies that bind and neutralize the virus. By the same mechanism, HIV infections cause other viruses in the individual to last longer and change. For example, herpes simplex virus can develop unusual drug resistance in AIDS patients.
Still, we need a better understanding of which immunocompromised patients are most vulnerable to long-term SARS-CoV-2 infection. The “immunocompromised” category thus encompasses a wide variety of different conditions, and they may not all present the same risk of persistent Covid-19. Brian Wasik, a virologist at Cornell University, points out that the term can include people born with rare conditions that impair their ability to fight pathogens, as well as those taking immunosuppressants to enable a transplant or an auto- suppress immune disease.
Evidence for the links between immunocompromised individuals and persistent SARS-CoV-2 infections, and between persistent infections and viral evolution, is compelling enough to be considered in discussions of vaccine priority. Sunday, a panel from the US Centers for Disease Control and Prevention recommended that immunocompromised people be placed in “Phase 1c” – the third wave – of the introduction of vaccines. That means they will get the injections at the same time as people with cancer, coronary artery disease, or obesity, among other conditions. That decision was designed to address the specific risks of Covid-19 to people with immune system problems, but it omitted the possibility that vaccinating these individuals could help prevent the development of new SARS-CoV-2 variants that could even affect this pandemic. would make. worse than it already is. For that reason, while there are only a handful of directly relevant case reports, public health officials should consult virologists about whether it is wise to move immunocompromised people to the earlier stage 1b group.
At the very least, we need better monitoring of possible changes in SARS-CoV-2. The US government should do more to help organize viral sequencing efforts. The CDC has a program nicknamed Spheres that attempted to capture sequence data during the pandemic, but it falls short: Where the UK has sequenced an estimated 10 percent of its Covid-19 cases, the US has only 0.3 percent managed. “It’s a bit patchy,” said Adam Lauring of the University of Michigan Medical School, who added that his team uploaded about 2 percent of sequence variant data in the US. “There are large parts of the country where not people spend a lot of time and effort on this task.” Better monitoring of viral evolution could also help clarify the question of where – in which sick people – these changes are most likely to accumulate.
While checking for SARS-CoV-2 mutations, we must recognize that understanding their epidemiological and clinical significance requires further work. Meanwhile, the virus is still proliferating, giving it more opportunities to mutate, even if it spreads from person to person. But the long-term infections in some immunocompromised individuals, and the associated potential for viral evolution, should be a concern.
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