COVID-19: answers to key questions about masks, mortality, and immunity

Takeaway

• Key COVID-19 questions about case fatality rate (CFR), reinfection, duration of immunity, and benefits of masks get answers in this JAMA minireview.

Why this matters

• The data may inform policy-making.

Key points

• CFR varies by location, from a high of 10.8% in Italy to a low of 0.7% in Germany.
• Can people become reinfected?
  • Some case reports from China and Japan indicated that patients who tested negative (RT-PCR test) at discharge could be readmitted with a positive test.
  • The best evidence suggests that reinfection does not occur until many months or years afterward, according to a challenge study of SARS-CoV-2 in rhesus macaques.
• How long does immunity last?
  • There are no long-term studies on SARS-CoV-2.
  • Long-term studies of SARS-CoV-1 indicate that titers of immunoglobulin G and neutralizing antibodies peak at 4 months postinfection, with a subsequent decrease during the next 3 years.
• Should everyone wear masks?
  • Everyone should wear masks that do not compete with N95 masks used by health care providers.
  • The primary reason is the potential for presymptomatic transmission.
  • Wearing masks only reduces risk that the wearer will transmit the virus and does not prevent healthy individuals from getting infected.
• SARS-CoV-2 spreads in droplets of 5-10 μm.