An apparent anti-masker replied to my story about masks on Instagram:

Q: allison bachmeier
Do you have studies proving efficacy?

A: Tracey TieF of @anarreshealth
They are certified by their manufacturers. N95 and KN95 are long standing standards that manufacturers must meet to certify their products.

Q:
But do you have studies was my question?

A:
I am a small apothecary. We do not commission studies.

Q:
I obviously don’t expect you to do the studies. I’m wondering about the research and the studies behind this product. Due diligence and all. Can you please share the studies?

A:
We buy from factories that display their third party certifications. The manufacturers don't themselves perform studies as to the efficacy of masks. Research leads to design specifications. Factories meet those design specifications, and third party certifiers verify that the factory's products meet the standard.

Q:
Wed 20:48
Vibrant Transformation
I understand how the process works. Due diligence means seeing studies, when buying anything medical/health in nature. If you’re unable to provide them then please be transparent in that you didn’t research it.

A:
I understand and support your concern. Please note, though, that nowhere do I advertise that I am selling medical masks. I am like zillions of other retailers, including all the major pharmacy chains, who do not make claims that are not directly from the manufacturer and imprinted on the product. I do have certificates as to the performance of ALL N95 and KN94 masks I sell. I truly do not understand what more you can expect from me.

A:
I might satisfy you by confessing that I have not researched the efficacy of masks, and N95 specifically, in mitigating the transmission of the SARS-COI-2 virus, however, alas, I have. I research many items of current concern on PubMed, aware that not all studies are of the same quality, and need peer review, and ultimately need to be repeated in order to see emerging truths. There is a difficulty in locating studies that are not super specific to workplaces and circumstances. This is because the basic efficacy of masks in mitigating droplet infection has been established for more than a hundred years. The fact that we cannot find studies on the effects of gravity does not mean that we don't fall down. It just means that science has moved on.

There are 926 studies that stand out when searching Pub Med. Is your question : Do masks work? Or: Does this retailer research all of the products she sells? Or perhaps you don't know how to search for the abstracts of published medical studies.

Here are some results, though.
1
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Masks or N95 Respirators During COVID-19 Pandemic-Which One Should I Wear?
Zhang M, Emery AR, Tannyhill RJ 3rd, Zheng H, Wang J.
J Oral Maxillofac Surg. 2020 Dec;78(12):2114-2127. doi: 10.1016/j.joms.2020.08.024. Epub 2020 Aug 27.
PMID: 32926868 Free PMC article. Review.
PURPOSE: Coronavirus Disease 2019 (COVID-19) has caused suffering and death around the world. ...CONCLUSION: N95 respirators are preferred over masks against viral respiratory pathogens, especially during aerosol-generating procedures or …

2
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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.
Chu DK, Akl EA, Duda S, Solo K, Yaacoub S, Schünemann HJ; COVID-19 Systematic Urgent Review Group Effort (SURGE) study authors.
Lancet. 2020 Jun 27;395(10242):1973-1987. doi: 10.1016/S0140-6736(20)31142-9. Epub 2020 Jun 1.
PMID: 32497510 Free PMC article.
BACKGROUND: Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) causes COVID-19 and is spread person-to-person through close contact. ...METHODS: We did a systematic review and meta-analysis to …

3
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Retracted: Facemasks in the COVID-19 era: A health hypothesis.
Vainshelboim B.
Med Hypotheses. 2021 Jan;146:110411. doi: 10.1016/j.mehy.2020.110411. Epub 2020 Nov 22.
PMID: 33303303 Free PMC article. Retracted. Review.
Many countries across the globe utilized medical and non-medical facemasks as non-pharmaceutical intervention for reducing the transmission and infectivity of coronavirus disease-2019 (COVID-19). Although, scientific evidence supporting facemasks' effi …

4
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Comprehensive review of mask utility and challenges during the COVID-19 pandemic.
Tirupathi R, Bharathidasan K, Palabindala V, Salim SA, Al-Tawfiq JA.
Infez Med. 2020 Jun 1;28(suppl 1):57-63.
PMID: 32532940 Free article. Review.
Masks are widely discussed during the course of the ongoing COVID-19 pandemic. Most hospitals have implemented universal masking for their healthcare workers, and the Center for Disease Control currently advises even the general public to wear cloth masks when outdo …

5
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Face masks vs. COVID-19: a systematic review.
Fouladi Dehaghi B, Ghodrati-Torbati A, Teimori G, Ibrahimi Ghavamabadi L, Jamshidnezhad A.
Invest Educ Enferm. 2020 Jul;38(2):e13. doi: 10.17533/udea.iee.v38n2e13.
PMID: 33047556 Free PMC article.
The coronavirus disease (COVID-19) spread rapidly around the world. Two types of approaches have been applied to use of face masks as a tool to prevent the spread this disease in society. ...Search terms were 'facemasks', 'novel coronavirus', and 'heal …

6
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Use of N95, Surgical, and Cloth Masks to Prevent COVID-19 in Health Care and Community Settings: Living Practice Points From the American College of Physicians (Version 1).
Qaseem A, Etxeandia-Ikobaltzeta I, Yost J, Miller MC, Abraham GM, Obley AJ, Forciea MA, Jokela JA, Humphrey LL; Scientific Medical Policy Committee of the American College of Physicians, Centor RM, Andrews R, Bledsoe TA, Haeme R, Kansagara DL, Marcucci M.
Ann Intern Med. 2020 Oct 20;173(8):642-649. doi: 10.7326/M20-3234. Epub 2020 Jun 18.
PMID: 32551813 Free PMC article. Review.
Controversy exists around the appropriate types of masks and the situations in which they should be used in community and health care settings for the prevention of SARS-CoV-2 infection. In this article, the American College of Physicians (ACP) provides recom …

7
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Effectiveness of Face Masks in Preventing Airborne Transmission of SARS-CoV-2.
Ueki H, Furusawa Y, Iwatsuki-Horimoto K, Imai M, Kabata H, Nishimura H, Kawaoka Y.
mSphere. 2020 Oct 21;5(5):e00637-20. doi: 10.1128/mSphere.00637-20.
PMID: 33087517 Free PMC article.
Guidelines from the CDC and the WHO recommend the wearing of face masks to prevent the spread of coronavirus (CoV) disease 2019 (COVID-19); however, the protective efficiency of such masks against airborne transmission of infectious severe …

8
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COVID-19 Autopsies, Oklahoma, USA.
Barton LM, Duval EJ, Stroberg E, Ghosh S, Mukhopadhyay S.
Am J Clin Pathol. 2020 May 5;153(6):725-733. doi: 10.1093/ajcp/aqaa062.
PMID: 32275742 Free PMC article.
OBJECTIVES: To report the methods and findings of two complete autopsies of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) positive individuals who died in Oklahoma (United States) in March 2020. METHODS …

9
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Challenges of COVID-19 in children in low- and middle-income countries.
Zar HJ, Dawa J, Fischer GB, Castro-Rodriguez JA.
Paediatr Respir Rev. 2020 Sep;35:70-74. doi: 10.1016/j.prrv.2020.06.016. Epub 2020 Jun 25.
PMID: 32654854 Free PMC article. Review.
As the coronavirus pandemic extends to low and middle income countries (LMICs), there are growing concerns about the risk of coronavirus disease (COVID-19) in populations with high prevalence of comorbidities, the impact on health and economies more br …

10
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COVID-19 in otolaryngologist practice: a review of current knowledge.
Krajewska J, Krajewski W, Zub K, Zatoński T.
Eur Arch Otorhinolaryngol. 2020 Jul;277(7):1885-1897. doi: 10.1007/s00405-020-05968-y. Epub 2020 Apr 18.
PMID: 32306118 Free PMC article. Review.
METHODS: The Medline and Web of Science databases were searched without a time limit using terms "COVID-19", "SARS-CoV-2" in conjunction with "otorhinolaryngological manifestation", "ENT", and "olfaction". ...ENT surgeons could be easily infecte …

11
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COVID-19 and Dentistry: Prevention in Dental Practice, a Literature Review.
Villani FA, Aiuto R, Paglia L, Re D.
Int J Environ Res Public Health. 2020 Jun 26;17(12):4609. doi: 10.3390/ijerph17124609.
PMID: 32604906 Free PMC article. Review.
SARS-CoV-2 is a member of the family of coronaviruses. The first cases were recorded in Wuhan, China, between December 2019 and January 2020. Italy is one of the most affected countries in Europe. COVID-19 is a new challenge in modern den …

12
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Current knowledge of COVID-19 and infection prevention and control strategies in healthcare settings: A global analysis.
Islam MS, Rahman KM, Sun Y, Qureshi MO, Abdi I, Chughtai AA, Seale H.
Infect Control Hosp Epidemiol. 2020 Oct;41(10):1196-1206. doi: 10.1017/ice.2020.237. Epub 2020 May 15.
PMID: 32408911 Free PMC article. Review.
OBJECTIVE: In the current absence of a vaccine for COVID-19, public health responses aim to break the chain of infection by focusing on the mode of transmission. ...We then compared these findings with the recommended IPC measures. RESULTS: Nosocomial transmission o …

13
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Decontamination and reuse of surgical masks and N95 filtering facepiece respirators during the COVID-19 pandemic: A systematic review.
Seresirikachorn K, Phoophiboon V, Chobarporn T, Tiankanon K, Aeumjaturapat S, Chusakul S, Snidvongs K.
Infect Control Hosp Epidemiol. 2021 Jan;42(1):25-30. doi: 10.1017/ice.2020.379. Epub 2020 Jul 30.
PMID: 32729444 Free PMC article.
OBJECTIVES: Surgical masks and N95 filtering facepiece respirators (FFRs) prevent the spread of severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) infection and protect medical personnel. Increased de …

14
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[SARS CoV-2/COVID-19: Evidence-Based Recommendation on Diagnosis and Therapy].
Bein B, Bachmann M, Huggett S, Wegermann P.
Anasthesiol Intensivmed Notfallmed Schmerzther. 2020 Apr;55(4):257-265. doi: 10.1055/a-1146-8674. Epub 2020 Apr 9.
PMID: 32274773 Free PMC article. Review. German.
COVID-19, a new viral disease affecting primarily the respiratory system and the lung, has caused a pandemic with serious challenges to health systems around the world. ...Therefore, during all procedures associated with aerosol production, a personal safety …

15
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COVID-19 coronavirus: recommended personal protective equipment for the orthopaedic and trauma surgeon.
Hirschmann MT, Hart A, Henckel J, Sadoghi P, Seil R, Mouton C.
Knee Surg Sports Traumatol Arthrosc. 2020 Jun;28(6):1690-1698. doi: 10.1007/s00167-020-06022-4. Epub 2020 Apr 27.
PMID: 32342138 Free PMC article. Review.
PURPOSE: With the COVID-19 crisis, recommendations for personal protective equipment (PPE) are necessary for protection in orthopaedics and traumatology. ...METHODS: A systematic review of the available literature was performed using the keyword terms "COVID- …

16
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High-Risk Aerosol-Generating Procedures in COVID-19: Respiratory Protective Equipment Considerations.
Howard BE.
Otolaryngol Head Neck Surg. 2020 Jul;163(1):98-103. doi: 10.1177/0194599820927335. Epub 2020 May 12.
PMID: 32396451 Review.
The correct selection and utilization of respiratory personal protective equipment is of the utmost importance in the current COVID-19 pandemic. ...For standard airborne precautions, N95 respirator are appropriate for respiratory protection. How …

17
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COVID-19, Personal Protective Equipment, and Human Performance.
Ruskin KJ, Ruskin AC, Musselman BT, Harvey JR, Nesthus TE, O'Connor M.
Anesthesiology. 2021 Apr 1;134(4):518-525. doi: 10.1097/ALN.0000000000003684.
PMID: 33404638 Free PMC article. Review.
Clinicians who care for patients infected with coronavirus disease 2019 (COVID-19) must wear a full suite of personal protective equipment, including an N95 mask or powered air purifying respirator, eye protection, a fluid-impermeable gown, and …

18
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Donning N95 respirator masks for COVID-19 prevention.
Joob B, Wiwanitkit V.
Braz J Anesthesiol. 2021 Sep-Oct;71(5):592. doi: 10.1016/j.bjane.2021.05.007. Epub 2021 Jun 9.
PMID: 34118258 Free PMC article. No abstract available.

19
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Face masks against COVID-19: Standards, efficacy, testing and decontamination methods.
Ju JTJ, Boisvert LN, Zuo YY.
Adv Colloid Interface Sci. 2021 Jun;292:102435. doi: 10.1016/j.cis.2021.102435. Epub 2021 Apr 29.
PMID: 33971389 Free PMC article. Review.
Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the virus responsible for the novel coronavirus disease 2019 (COVID-19), has caused a global pandemic on a scale not seen for o …

20
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Why N95 Should Be the Standard for All COVID-19 Inpatient Care.
Dau NQ, Peled H, Lau H, Lyou J, Skinner C.
Ann Intern Med. 2020 Nov 3;173(9):749-751. doi: 10.7326/M20-2623. Epub 2020 Jun 29.
PMID: 32598163 Free PMC article.
Guidelines differ in their guidance on the use of N95 respirators versus medical masks for frontline health care workers working with patients with COVID-19, particularly when aerosolized procedures are not involved. This article makes the case that the exist …

21
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Multidisciplinary Safety Recommendations After Tracheostomy During COVID-19 Pandemic: State of the Art Review.
Meister KD, Pandian V, Hillel AT, Walsh BK, Brodsky MB, Balakrishnan K, Best SR, Chinn SB, Cramer JD, Graboyes EM, McGrath BA, Rassekh CH, Bedwell JR, Brenner MJ.
Otolaryngol Head Neck Surg. 2021 May;164(5):984-1000. doi: 10.1177/0194599820961990. Epub 2020 Sep 22.
PMID: 32960148 Free PMC article. Review.
REVIEW METHODS: Literature through June 2020 on the care of patients with a tracheostomy was reviewed, including consensus statements, clinical practice guidelines, institutional guidance, and scientific literature on COVID-19 and SARS-CoV-2 vir …

22
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The COVID-19 pandemic, personal protective equipment and respirator: A narrative review.
Ha JF.
Int J Clin Pract. 2020 Oct;74(10):e13578. doi: 10.1111/ijcp.13578. Epub 2020 Jun 28.
PMID: 32511834 Free PMC article. Review.
INTRODUCTION: The coronavirus disease 2019 pandemic has touched almost every continent. ...METHOD: A literature search was conducted on the PubMed, MedLine and Embase databases with the keywords "personal protective equipment," "COVID 19," "n95, …

23
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Protection From COVID-19-The Efficacy of Face Masks.
Hemmer CJ, Hufert F, Siewert S, Reisinger E.
Dtsch Arztebl Int. 2021 Feb 5;118(5):59-65. doi: 10.3238/arztebl.m2021.0119.
PMID: 33785117 Free PMC article.
BACKGROUND: Since the beginning of 2020 the SARS-CoV-2 virus has spread to nearly every country in the world. ...No randomized trials have been conducted on the effect of masks covering the mouth and nose. A metaanalysis of 29 studies on infection with SAR …

24
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The adverse skin reactions of health care workers using personal protective equipment for COVID-19.
Hu K, Fan J, Li X, Gou X, Li X, Zhou X.
Medicine (Baltimore). 2020 Jun 12;99(24):e20603. doi: 10.1097/MD.0000000000020603.
PMID: 32541493 Free PMC article.
On February 11, the World Health Organization (WHO) officially named the disease caused by 2019-nCoV coronavirus disease 2019 (COVID-19). With the increasing number of cases, health care workers (HCWs) from all over China volunteered to w …

25
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Approaching Otolaryngology Patients During the COVID-19 Pandemic.
Cui C, Yao Q, Zhang D, Zhao Y, Zhang K, Nisenbaum E, Cao P, Zhao K, Huang X, Leng D, Liu C, Li N, Luo Y, Chen B, Casiano R, Weed D, Sargi Z, Telischi F, Lu H, Denneny JC 3rd, Shu Y, Liu X.
Otolaryngol Head Neck Surg. 2020 Jul;163(1):121-131. doi: 10.1177/0194599820926144. Epub 2020 May 12.
PMID: 32396445 Free PMC article.
Objective. To describe coronavirus disease 2019 (COVID-19) patient presentations requiring otolaryngology consultation and provide recommendations for protective measures based on the experience of ear, nose, and throat (ENT) departments in 4 Chinese h …

26
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Covid-19: countermeasure for N95 mask-induced pressure sore.
Yin ZQ.
J Eur Acad Dermatol Venereol. 2020 Jul;34(7):e294-e295. doi: 10.1111/jdv.16490. Epub 2020 May 27.
PMID: 32302449 Free PMC article. No abstract available.

27
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[Masks as personal protective equipment in the COVID-19 pandemic: How, when and which should be used].
Aranaz Andrés JM, Gea Velázquez de Castro MT, Vicente-Guijarro J, Beltrán Peribáñez J, García Haro M, Valencia-Martín JL, Bischofberger Valdés C; Grupo de Trabajo COVID-19 del Hospital Universitario Ramón y Cajal; Grupo de Trabajo COVID-19 del Hospital Universitario Ramón y Cajal.
J Healthc Qual Res. 2020 Jul-Aug;35(4):245-252. doi: 10.1016/j.jhqr.2020.06.001. Epub 2020 Jun 25.
PMID: 32680724 Free PMC article. Spanish.
BACKGROUND AND OBJECTIVE: In the COVID-19 pandemic, the demand of masks has been increased by health professionals and the general population. ...CONCLUSION: In the context of shortage of personal protective equipment due to the COVID-19 pandemic, a pr …

28
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Covid-19 and the N95 respirator shortage: Closing the gap.
Nogee D, Tomassoni AJ.
Infect Control Hosp Epidemiol. 2020 Aug;41(8):958. doi: 10.1017/ice.2020.124. Epub 2020 Apr 13.
PMID: 32279694 Free PMC article.
Due to extreme shortages of personal protective equipment caused by the COVID-19 pandemic, many healthcare workers will be forced to recycle protective masks intended for disposal after a single use. We propose investigating the use of ultraviolet germicidal irradia …

29
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N95 respirator, COVID-19, and health care worker.
Wiwanitkit V.
Int Wound J. 2020 Oct;17(5):1534. doi: 10.1111/iwj.13419. Epub 2020 Jun 2.
PMID: 32488933 Free PMC article. No abstract available.

30
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Critical Care Guidance for Tracheostomy Care During the COVID-19 Pandemic: A Global, Multidisciplinary Approach.
Pandian V, Morris LL, Brodsky MB, Lynch J, Walsh B, Rushton C, Phillips J, Rahman A, DeRose T, Lambe L, Lami L, Wu SPM, Garza FP, Maiani S, Zavalis A, Okusanya KA, Palmieri PA, McGrath BA, Pelosi P, Sole ML, Davidson P, Brenner MJ.
Am J Crit Care. 2020 Nov 1;29(6):e116-e127. doi: 10.4037/ajcc2020561.
PMID: 32929453 Review.
PURPOSE: Critical care nurses caring for patients with a tracheostomy are at high risk because of the predilection of SARS-CoV-2 for respiratory and mucosal surfaces. This review identifies patient-centered practices that ensure safety and reduce risk …

There are 90 more pages of relevant results, so you might want to search yourself. Just go to PubMed.gov and search "N95 covid-19". But if you wanted to know if I had researched N95, then yes, yes I have! And they help.