ACP Living Practice Points: Emerging evidence on antibody response and role in natural immunity

PHILADELPHIA, March 16, 2021 – In new Rapid Living Practice Points, the American College of Physicians (ACP) summarizes the current, best available evidence on the antibody response to SARS-CoV-2 infection, including its duration and protection against future re-infection. The new Rapid Living Practice Points, developed by the Scientific Medical Policy Committee of the ACP, What is the Antibody Response and Role in Conferring Natural Immunity Following SARS-CoV-2 Infection? Rapid, Living Practice Points from the American College of Physicians (Version 1) was published today in Annals of Internal Medicine.

The ACP Practice Points provide clinical advice, based on the best available current evidence, on the use of antibody tests for the diagnosis of SARS-CoV-2 infection and as an indicator of natural immunity against the infection. The Practice Points also address the use of the antibody tests for determining community prevalence of SARS-CoV-2 infections. The Practice Points are based on a rapid review conducted by AHRQ Evidence-based Practice Center Program’s Scientific Resource Center at the Portland VA Research Foundation. This paper only evaluates natural immunity; it does not evaluate artificial immunity conferred by vaccines or cellular immunity, both of which are important areas of future research.

The widespread availability of SARS-CoV-2 antibody tests has raised important questions for clinicians, patients, and public health professionals related to their appropriate use and interpretation of the results. Currently, little is known about the relationship between SARS-CoV-2 antibodies and natural immunity. As with other viruses, the relationship between antibodies and natural immunity varies based on a number of factors.

The ACP’s Practice Points say:

  • Do not use SARS-CoV-2 antibody tests for the diagnosis of SARS-CoV-2 infection.
  • Antibody tests can be useful for the purpose of estimating community prevalence of SARS-CoV-2 infection.
  • Current evidence is uncertain to predict presence, level, or durability of natural immunity conferred by SARS-CoV-2 antibodies against re-infection (following SARS-CoV-2 infection).

“The availability of COVID-19 antibody tests raises critical questions as to their use and how they are interpreted by clinicians and ultimately for advising patients,” said Jacqueline W. Fincher, MD, MACP, president, ACP. “Once a patient has tested positive for SARS-CoV-2 infection, the questions remain as to whether or not they will be protected from reinfection, how long antibody protection lasts and to what level.”

“Until more is known, I encourage my patients to continue to protect themselves with the 3 Ws – wash your hands, watch your distance and wear a mask when indoors or cannot socially distance,” added Dr. Fincher.

As more information emerges on SARS-CoV-2 and vaccines are developed, health officials still urge caution in the face of uncertainty about the infection. It is recommended that patients with SARS-CoV-2 infection, patients with history of SARS-CoV-2 infection, and the public, follow recommended infection prevention and control procedures and preventive measures to slow and reduce the transmission of SARS-CoV-2 infection, including maintaining physical distance, wearing face coverings such as surgical or cloth masks in settings where physical distancing is not possible, appropriate mask use, self-isolation, quarantine, frequent hand hygiene (using soap and water or alcohol-based hand rub), covering cough and sneezes using a bent elbow or paper tissue, refraining from touching the face, and frequent  disinfection of frequently touched surfaces.

ACP’s Practice Points are developed by ACP’s Scientific Medical Policy Committee and provide advice to improve the health of individuals and populations and promote high value care based on the best available evidence derived from assessment of scientific work (e.g. clinical guidelines, systematic reviews, individual studies). ACP Practice Points aim to address the value of screening and diagnostic tests and therapeutic interventions for various diseases, and consider known determinants of health, including but not limited to genetic variability, environment, and lifestyle.

The ACP Practice Points will be maintained as a “living” document and ACP’s Scientific Medical Policy Committee will monitor emerging evidence to determine its impact on the main findings and conclusions, and issue updates as needed.

“These Practice Points shed important light on this emerging topic. However, significant evidence gaps remain and additional research and studies are needed to evaluate the protection these tests provide and to further understand how variability of patient demographics can impact results,” added Dr. Fincher.


About the American College of Physicians
The American College of Physicians is the largest medical specialty organization in the United States with members in more than 145 countries worldwide. ACP membership includes 163,000 internal medicine physicians (internists), related subspecialists, and medical students. Internal medicine physicians are specialists who apply scientific knowledge and clinical expertise to the diagnosis, treatment, and compassionate care of adults across the spectrum from health to complex illness. Follow ACP on Twitter, Facebook and Instagram.

ACP Media Contact: Andrew Hachadorian, (215) 351-2514,