The study examines the effectiveness of masks and of following a hand hygiene program in reducing the likelihood of acquiring respiratory virus infections such as COVID-19.

British Health Researcher Dr. John Campbell shares the disappointing results in this presentation:

From Dr. John Campbell

From the Cochrane Library

What did we do?
We searched for randomised controlled studies that looked at physical measures to stop people acquiring a respiratory virus infection.

We were interested in how many people in the studies caught a respiratory virus infection, and whether the physical measures had any unwanted effects.

What did we find?
We identified 78 relevant studies. They took place in low‐, middle‐, and high‐income countries worldwide: in hospitals, schools, homes, offices, childcare centres, and communities during non‐epidemic influenza periods, the global H1N1 influenza pandemic in 2009, epidemic influenza seasons up to 2016, and during the COVID‐19 pandemic. We identified five ongoing, unpublished studies; two of them evaluate masks in COVID‐19. Five trials were funded by government and pharmaceutical companies, and nine trials were funded by pharmaceutical companies.

We assessed the effects of:

· medical or surgical masks;

· N95/P2 respirators (close‐fitting masks that filter the air breathed in, more commonly used by healthcare workers than the general public); and

· hand hygiene (hand‐washing and using hand sanitiser).

We obtained the following results:

Medical or surgical masks

Ten studies took place in the community, and two studies in healthcare workers. Compared with wearing no mask in the community studies only, wearing a mask may make little to no difference in how many people caught a flu‐like illness/COVID‐like illness (9 studies; 276,917 people); and probably makes little or no difference in how many people have flu/COVID confirmed by a laboratory test (6 studies; 13,919 people). Unwanted effects were rarely reported; discomfort was mentioned.

N95/P2 respirators

Four studies were in healthcare workers, and one small study was in the community. Compared with wearing medical or surgical masks, wearing N95/P2 respirators probably makes little to no difference in how many people have confirmed flu (5 studies; 8407 people); and may make little to no difference in how many people catch a flu‐like illness (5 studies; 8407 people), or respiratory illness (3 studies; 7799 people). Unwanted effects were not well‐reported; discomfort was mentioned.

Hand hygiene

Following a hand hygiene programme may reduce the number of people who catch a respiratory or flu‐like illness, or have confirmed flu, compared with people not following such a programme (19 studies; 71,210 people), although this effect was not confirmed as statistically significant reduction when ILI and laboratory‐confirmed ILI were analysed separately. Few studies measured unwanted effects; skin irritation in people using hand sanitiser was mentioned.

Dr. John Campbells presentation notes with links:

RCTs did not show a clear reduction in respiratory viral infection with the use of medical/surgical masks.

There were no clear differences between the use of medical/surgical masks compared with N95/P2 respirators in healthcare workers, when used in routine care to reduce respiratory viral infection.

Do physical measures such as hand-washing or wearing masks stop or slow down the spread of respiratory viruses?

https://www.cochranelibrary.com/cdsr/…

Evidence published up to October 2022.

Background Influenza (H1N1) caused by the H1N1pdm09 virus in 2009

Severe acute respiratory syndrome (SARS) in 2003 Coronavirus disease 2019 (COVID-19)

Update of a Cochrane Review last published in 2020.

We include results from studies from the current COVID-19 pandemic.

Main results 11 new RCTs and cluster-RCTs n = 610,872

Bringing the total number of RCTs to 78

Medical/surgical masks compared to no masks

Wearing masks in the community probably makes little or no difference to the outcome of influenza‐like illness

wearing a mask may make little to no difference in how many people caught a flu-like illness/COVID-like illness

Risk ratio (RR) 0.95, (0.84 to 1.09) 9 trials, n = 276,917 participants

Moderate-certainty evidence.

Wearing masks in the community probably makes little or no difference to the outcome of laboratory-confirmed influenza/SARS-CoV-2 RR 1.01, (CI 0.72 to 1.42)

6 trials, n = 13,919 Moderate-certainty evidence

Harms were rarely measured and poorly reported (very low-certainty evidence).

N95/P2 respirators compared to medical/surgical masks

We pooled trials comparing N95/P2 respirators with medical/surgical masks

We are very uncertain on the effects of N95/P2 respirators compared with medical/surgical masks on the outcome of clinical respiratory illness

Compared with wearing medical or surgical masks, wearing N95/P2 respirators probably makes little to no difference in how many people have confirmed flu and may make little to no difference in how many people catch a flu-like illness, or respiratory illness.

Confirmed influenza RR 0.70, (0.45 to 1.10) N = 7,779 Very low-certainty evidence

Influenza like illness N95/P2 respirators compared with medical/surgical masks may be effective for ILI RR 0.82 N= 8,407 Low-certainty evidence

The use of a N95/P2 respirators compared to medical/surgical masks

Probably makes little or no difference for laboratory-confirmed influenza infection RR 1.10 N = 8,407 Moderate-certainty evidence

Restricting pooling to healthcare workers made no difference to the overall findings.

Harms were poorly measured and reported

Discomfort wearing medical/surgical masks or N95/P2 respirators was mentioned in several studies

Very low-certainty evidence

One new RCT Medical/surgical masks were non-inferior to N95 respirators N = 1,009 healthcare workers in four countries, providing direct care to COVID-19 patients.