In This Article
- Although definitive studies are needed, multiple lines of experimental evidence suggest humans will develop protective immunity to SARS-CoV-2 and will not be susceptible to rapid reinfection
- Immunity to SARS-CoV-2 may wane with time, although the duration is unknown and may be related, in part, to the severity of COVID-19
- If SARS-CoV-2 establishes within the human population, a vaccine will be needed for both naive individuals and survivors of COVID-19 with waning immunity
- A SARS-CoV-2 vaccine will not be available during the first wave of the COVID-19 pandemic, but six approaches to vaccine development are being pursued, some with the potential for more rapid large-scale production
People infected with SARS-CoV-2 will likely develop protective immunity, evidence suggests, but it may wane over time. Rod Rahimi, MD, PhD, of the Division of Pulmonary and Critical Care Medicine at Massachusetts General Hospital, discusses these issues and vaccine development in a fast literature update posted on April 24, 2020.
Potential for Immunity
Three lines of evidence suggest people will be protected from rapid reinfection with SARS-CoV-2:
- Humans develop protective immunity from non-SARS coronaviruses that cause mild respiratory infections
- Individuals who recovered from SARS or MERS demonstrated antigen-specific immune memory
- Macaques re-challenged with SARS-CoV-2 a month after infection did not become reinfected
Popular media have reported on individuals recovering from COVID-19 who had a negative PCR test followed by a positive test. The claims have been that these people became reinfected or had the virus "re-activated." However, all of these people remained asymptomatic. They almost certainly had false-negative results, then true-positive results due to ongoing viral RNA shedding during the recovery period.
Duration of Immunity
The author notes:
- Experiments with non-SARS coronaviruses suggest immunity may wane after one year
- Among survivors of SARS and MERS, viral-specific antibodies wane significantly after two years, but individuals who needed ICU care or mechanical ventilation seem to exhibit more long-lasting immunity
- If SARS-CoV-2 establishes within the human population, a vaccine will be needed to protect both naïve individuals and survivors of COVID-19 who have waning immunity.
Six strategies, detailed in the literature update, are being used to develop a SARS-CoV-2 vaccine. An mRNA vaccine is in a phase I trial, and a phase I trial recently began enrolling for one of the multiple DNA vaccine candidates. The oft-cited figures are probably accurate: a vaccine is 12 to 18 months away.
An RNA or DNA vaccine would be suitable for integration into generic manufacturing platforms for quicker mass production. However, no RNA or DNA vaccine for any pathogen has reached the market yet, so the safety and efficacy of these approaches will face additional hurdles.
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