Spanish flu;

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?

Why might convalescent sera or plasma transfusion therapy be effective in the treatment of patients with Covid-19?

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

Of the myriad therapeutic approaches currently under consideration in our fight against Covid-19, convalescent sera/plasma therapy (CSPT) is particularly promising. The principle behind CSPT is to provide immediate immunity to susceptible people by administering the serum or plasma—therefore antibodies—of individuals who have successfully recovered from Covid-19.1

The theory behind using antibody-containing blood products to treat infections is by no means new and goes back to the 1890s when serum from exposed animals who recovered from disease was used to protect healthy animals against tetanus and diphtheria.2

Historically, CSPT has been used against poliomyelitis, measles, mumps, and influenza, and more recently in a smaller number of patients with SARS, H5N1 and H7N9 avian influenza and Ebola.1,3-8 A 2015 systematic review and exploratory meta-analysis of 32 studies involving severe acute respiratory infections of viral etiology (including influenza and SARS) found a reduction in mortality (odds ratio, 0.25, 95% C.I. 0.14-0.45), particularly when CSPT was administered early into the illness.3

Experience with 1918 Spanish influenza pandemic: A meta-analysis of 1703 hospitalized patients (Yes, scientists performed wonderful studies back then too despite a pandemic!) during the 1918 Spanish influenza pandemic demonstrated decreased mortality with administration of convalescent blood products with crude case-fatality rates dropping by one-half (16% vs 37% in controls)! Notably, patients who were treated within 4 days of pneumonia had one-third the case-fatality rate compared to those treated later.3

Experience with 2002-2004 SARS epidemic: A retrospective study from Hong Kong involving 80 patients with SARS (caused by another coronavirus, SARS-CoV-1) not responding to antibiotics/steroids/interferon but receiving CSPT reported a lower mortality rate with near significant (P=0.08) improvement in outcome and reduced mortality in the group that received CSPT before day 14 of the illness (6.3% vs 21.9%).4

What about Covid-19? A very preliminary report out of China involving 5 mechanically-ventilated patients with ARDS and rapid progression despite corticosteroids and antivirals found clinical improvement in all 5 patients. More specifically, body temperature normalized within 3 days in 4 of 5 patients and ARDS resolved in 4 patients at 12 days following transfusion, 2 patients were in stable condition and 3 patients were eventually discharged from the hospital.9

Of course, we should be mindful of potential adverse reactions due to CSP as well, such as allergic reactions, infections, transfusion-related acute lung injury (TRALI), and theoretical risk of antibody-dependent enhancement of infection (ADE).1 Only properly designed clinical studies can shed light on the safety and efficacy of CSPT in Covid-19.

Nevertheless, the historical data on the use of CSPT in serious viral infections is encouraging. In fact, the first US studies of CSPT in Covid-19 have already been approved by the FDA!10 Stay tuned!

Bonus pearl: Did you know that serum and plasma both refer to the noncellular fluid part of blood, but serum is collected after coagulation factors (fibrinogen) have been removed. Fortunately, both contain antibodies!

 

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Contributed by Bruce Tiu, Harvard Medical Student, Boston, MA.

References:

  1. Casadevall A, Pirofski L. The convalescent sera for containing COVID-19. J Clin Invest. 2020;130(4):1545-1548. doi: 10.1172/JCI138003 https://www.jci.org/articles/view/138003
  2. Eibl MM. History of immunoglobulin replacement. Immunol Allergy Clin North Am. 2008;28(4):737–viii. doi:10.1016/j.iac.2008.06.004 https://www.sciencedirect.com/science/article/abs/pii/S0889856108000702
  3. Mair-Jenkins J, Saavedra-Campos M, Baillie K, et al. The effectiveness of convalescent plasma and hyperimmune immunoglobulin for the treatment of severe acute respiratory infections of viral etiology: A systematic review and exploratory meta-analysis. J Infect Dis 2015; 211: 80-90. https://academic.oup.com/jid/article/211/1/80/799341
  4. Luke TC, Kilbane EM, Jackson JL, et al. Meta-Analysis: Convalescent Blood Products for Spanish Influenza Pneumonia: A Future H5N1 Treatment?. Ann Intern Med. 2006;145:599–609. doi: 10.7326/0003-4819-145-8-200610170-00139 https://annals.org/aim/article-abstract/729754/meta-analysis-convalescent-blood-products-spanish-influenza-pneumonia-future-h5n1
  5. Cheng Y, Wong R, Soo YO, et al. Use of convalescent plasma therapy in SARS patients in Hong Kong. Eur J Clin Microbiol Infect Dis. 2005;24(1):44–46. doi:10.1007/s10096-004-1271-9 https://link.springer.com/article/10.1007/s10096-004-1271-9
  6. Zhou B, Zhong N, Guan Y. Treatment with convalescent plasma for influenza A (H5N1) infection. N Engl J Med. 2007;357:1450–1. doi: 10.1056/NEJMc070359 https://www.nejm.org/doi/full/10.1056/NEJMc070359
  7. Chen L, Xiong J, Bao L, et al. Convalescent plasma as a potential therapy for COVID-19. Lancet Infect Dis 2020;20: 398-400. https://www.thelancet.com/journals/laninf/article/PIIS1473-3099(20)30141-9/fulltext
  8. Wu XX, Gao HN, Wu HB, Peng XM, Ou HL, Li LJ. Successful treatment of avian-origin influenza A (H7N9) infection using convalescent plasma. Int J Infect Dis. 2015;41:3–5. doi: 10.1016/j.ijid.2015.10.009 https://www.ncbi.nlm.nih.gov/pubmed/26482389
  9. Shen C, Wang Z, Zhao F, et al. Treatment of 5 Critically Ill Patients With COVID-19 With Convalescent Plasma. JAMA. Published online March 27, 2020. doi:10.1001/jama.2020.4783 https://jamanetwork.com/journals/jama/fullarticle/2763983
  10. https://thehill.com/regulation/healthcare/490768-first-us-coronavirus-patients-being-treated-with-plasma-therapy.

Disclosures: The listed questions and answers are solely the responsibility of the author and do not necessarily represent the official views of Massachusetts General Hospital, Harvard Catalyst, Harvard University, its 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!

 

 

 

 

Why might convalescent sera or plasma transfusion therapy be effective in the treatment of patients with Covid-19?