Face masks

Who should get tested after a holiday indoor gathering with family members?

FA Manian MD, MPH, , , , , , , , , , , , Leave a comment

Whether you should get tested after holiday gatherings depends a lot on factors such as the level of transmission of Covid-19 within your region, the vaccination status of all the attendees, the likelihood of Covid-19 in any of the attendees, and your threshold for risk of either contracting or transmitting of Covid-19 to others, particularly immunocompromised persons. 

The following discussion assumes a scenario that is common to most indoor holiday gatherings: 1. You are getting together with people outside of your household; 2.  You or your family members don’t wear a face mask at all or certainly not all the time during the gathering; and 3. You find it impossible or don’t wish to socially distance from others during the get-together.1,2

First, let’s start with 2 situations where you should get tested following a holiday get-together, irrespective of your (or the attendees’) vaccination status: 1. if you have symptoms of Covid-19; and 2. If you were in close contact of an infected person (ie, commonly defined as within 6 feet of that person for a minimum of 15 minute during a 24-hour period).3

In the absence of known exposure or symptoms, you should consider getting tested if you are not fully immunized since you will be at higher risk of contracting and transmitting Covid-19 to others as long as there is still significant Covid-19 transmission in the region.  In contrast, if you and other attendees are fully immunized already, routine testing for Covid-19 after the gathering is hard to justify given the effectiveness of FDA-authorized Covid-19 vaccines and the costs and impracticalities associated with routine testing of millions of fully vaccinated persons.  

It goes without saying that holiday gatherings with family members outside of one’s immediate houseshold is not a zero-risk proposition for contracting or transmitting Covid-19 because people can have no symptoms and be infectious and vaccinated individuals can on occasion become infected.   Even the tests are not perfect. However, if you are concerned that you might have been exposed to Covid-19  and knowledge of a negative Covid-19 test (with its inherent limitations) gives you peace of mind, you should consider getting tested. The over-the-counter rapid Covid-19 tests may be particularly useful in assessing the likelihood of being contagious.4

For further recommendations on when you should consider getting tested for Covid-19 in general, I highly recommend an NIH-sponsored online calculator called “When to Test”.  This calculator is based on mathematical modelling that takes into account an individual’s vaccination status, transmission rates in the geographic area, and mitigation behaviors (eg, masks and social distancing).1

Bonus Pearl: Did you know that persons with Covid-19 are considered infectious 2 days before they develop symptoms or 2 days before the date of their positive test if they don’t have symptoms?5

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References:

  1. When to test offers free online tool to help individuals make informed Covid-19 testing decisions. https://www.nih.gov/news-events/news-releases/when-test-offers-free-online-tool-help-individuals-make-informed-covid-19-testing-decisions. Accessed November 26, 2021.
  2. Covid-19 testing overview. https://www.cdc.gov/coronavirus/2019-ncov/symptoms-testing/testing.html. Accessed November 26, 2021.
  3. Covid-19. https://www.cdc.gov/coronavirus/2019-ncov/php/contact-tracing/contact-tracing-plan/appendix.html#contact. Accessed November 26, 2021.
  4. Schuit E, Venekamp RP, Pas SD, et al. Diagnostic accuracy of rapid antigen tests in asymptomatic and presymptomatic close contacts of individuals with confirmed SARS-CoV-2 infection: cross sectional study. BMJ 2021;374:n1676.  https://www.bmj.com/content/374/bmj.n1676
  5. Quarantine and isolation. https://www.cdc.gov/coronavirus/2019-ncov/your-health/quarantine-isolation.html#:~:text=Get%20tested%205%2D7%20days%20after%20their%20first%20exposure.,the%20person%20with%20COVID%2D19. Accessed November 26, 2021.

Disclosures: The listed questions and answers are solely the responsibility of the author and do not necessarily represent the official views of Mercy Hospital-St. Louis, Massachusetts General Hospital, Harvard Catalyst, Harvard University, their affiliate academic healthcare centers, or its contributors. Although every effort has been made to provide accurate information, the author is far from being perfect. The reader is urged to verify the content of the material with other sources as deemed appropriate and exercise clinical judgment in the interpretation and application of the information provided herein. No responsibility for an adverse outcome or guarantees for a favorable clinical result is assumed by the author. Thank you!

 

Who should get tested after a holiday indoor gathering with family members?

How effective are face masks in reducing transmission of Covid-19?

FA Manian MD, MPH, , , , , , , , , , , Leave a comment

Overall, review of data to date suggests that face masks are quite effective in reducing the transmission of coronaviruses, including SARS-CoV-2, the cause of Covid-19. A Lancet 2020 meta-analysis involving over 12,000 subjects, found that transmission of coronaviruses (SARS-CoV-2, SARS and MERS) was reduced with face masks by 85% (adjusted O.R. 0.15, 95%CI 0.07-0.34).1

More specific to Covid-19, a study from Mass General Brigham hospitals found a significant drop in healthcare worker (HCW) SARS-CoV-2 PCR positivity rate from 21.3% to 11.5% following adoption of universal masking of HCWs and patients.2

An U.S. epidemiologic survey of 2,930 unique counties plus New York City found mandating face mask use in public was associated with a significant decline in the daily Covid-19 growth rate. 3 It was estimated that more than 200,000 Covid-19 cases were averted by May 22, 2020 as a result of the implementation of these mandates.

Another 2020 meta-analysis involving 21 studies reported an overall efficacy of masks (including surgical and N-95 masks) of 80% in healthcare workers and 47% in non-healthcare workers for respiratory virus transmission (including SARS, SARS-CoV-2 and influenza).4

A criticism of above reports has been their primarily retrospective nature. A randomized-controlled Danish study found a statistically insignificant 20% reduction in incident SARS-CoV-2 infection among mask wearers (5,6).    Despite its randomized-controlled design, this study had several limitations, including relatively low transmission rate in the community and lack of universal mask wearing in public during the study period. In addition, less than one-half of participants in the mask group reported adherence to wearing masks, and there was no assurance that masks were worn correctly when they did wear them. 

At most, this study suggests that it’s not enough for the uninfected to wear masks; the infected—often with little or no symptoms— should also wear them to help curb the pandemic.

So please do your part and tell your friends and family members to do the same by masking up while we are at war with Covid-19!

Bonus Pearl: Did you know that universal wearing of masks in the public in response to a respiratory virus pandemic is nothing new?  It was adopted as far back as 100 years ago during the 1918 Spanish influenza pandemic!

References

  1. Chu DK, Akl EA, Duda S, et al. Physical distancing, face masks, and eye protection to prevent person-to-person transmission of SARS-CoV-2 and COVID-19: a systematic review and meta-analysis. Lancet 2020;395: 1973-87. https://www.thelancet.com/pdfs/journals/lancet/PIIS0140-6736(20)31142-9.pdf
  2. Wang X, Ferro EG, Zhou G, et al. Association between universal masking in a health care system and SARS-CoV-2 positivity among health care workers. JAMA 2020;324:703-4. https://jamanetwork.com/journals/jama/fullarticle/2768533
  3. Lyu W, Wehby GL. Community use of face masks and COVID-19: evidence from a natural experiment of state mandates in the US. Health Affairs 2020;39: July 16. https://www.healthaffairs.org/doi/full/10.1377/hlthaff.2020.00818
  4. Liang M, Gao L, Cheng Ce, et al. Efficacy of face mask in preventing respiratory virus transmission: A systematic review and meta-analysis. Travel Med Infect Dis 2020;36:1-8. https://pubmed.ncbi.nlm.nih.gov/32473312/ 
  5. Bundgaard H, Bundgaard JS, Tadeusz DE, et al. Effectiveness of adding a mask recommendation to other public health measures to prevent SARS-CoV-2 infection in Danish mask wearers. Ann Intern Med 2020; November 18. https://pubmed.ncbi.nlm.nih.gov/33205991/
  6. Frieden TR Cash-Goldwasser S. Of masks and methods. Ann Intern Med 2020; November 18. https://www.acpjournals.org/doi/10.7326/m20-7499

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Disclosures: The listed questions and answers are solely the responsibility of the author and do not necessarily represent the official views of Mercy Hospital-St. Louis or its affiliate healthcare centers. Although every effort has been made to provide accurate information, the author is far from being perfect. The reader is urged to verify the content of the material with other sources as deemed appropriate and exercise clinical judgment in the interpretation and application of the information provided herein. No responsibility for an adverse outcome or guarantees for a favorable clinical result is assumed by the author. Thank you!

How effective are face masks in reducing transmission of Covid-19?