The UK Health Security Agency (UKHSA) on Wednesday said it couldn’t find evidence on whether N95 or similar masks can protect clinically vulnerable people from getting serious illness from COVID-19.

Unlike a regular loose-fitting surgical mask, an N95 respirator is designed to fit tightly to form a seal around the nose and mouse. It’s also very efficient in filtering airborne particles.

In a previous publication on the effectiveness of face coverings, the UKHSA said that low-quality evidence suggested N95 respirators (or equivalent) may be more effective than surgical masks in preventing the wearer from being infected with coronavirus in healthcare settings.

But in a rapid review (pdf) published on Wednesday, the UKHSA said it had screened thousands of primary studies on the effectiveness of face coverings during the COVID-19 pandemic and couldn’t find a single one on whether wearing N95 and equivalent respirators in the community can protect people at higher risk from becoming seriously ill from COVID-19.

Researchers at the government agency screened studies some 50 studies were published by Sept. 14, 2021, and had previously been examined in a separate UKHSA review on the effectiveness of all face coverings in all people against transmission of COVID-19.

They also searched for papers and preprints published by Sept. 26, 2022, identifying a further 4,371 studies, but none looked at the efficacy of the specific type of masks in protecting the cohort.

“No studies matching the inclusion criteria were found, so no evidence could be presented,” the review concluded.

It noted that researchers didn’t include evidence from other infectious disease such as influenza, and that they didn’t conduct an extensive search of sources other than databases of peer-reviewed and preprint articles.

It also noted that a previous rapid review concluded that face coverings in general can reduce the spread of COVID-19 in the community.

Commenting on the review, Carl Heneghan, professor of evidence-based medicine at the University of Oxford, told The Telegraph that scientists “completely failed to address this issue.”

“I do not understand why there’s been a lack of will to do high-quality trials in this area,” he told the publication.

“For those people at low risk, these questions don’t necessarily matter too much, but if you’re at high risk, you really want this question to be addressed. You want to know the answer,” he said.

Heneghan said he believes it’s a failure that should be examined by the government-commissioned independent COVID-19 inquiry so the lesson can be leaned.

Mask-wearing, especially mask mandates for all, is one of the controversial restrictions that was deployed in many countries during the COVID-19 pandemic.

Some studies suggested that masks are effective in preventing COVID-19 transmission, while some question the amount of benefit.

Dr. Ashish Jha, the White House’s COVID-19 coordinator, said in December last year that there had been “no study in the world that shows that masks work that well.”

Apart from arguments around the benefits and harms of wearing masks, the issue of mask-wearing has also become a political issue during the pandemic following masking mandates.

The reluctance towards mask-wearing in the Western world has often been attributed to the populaces’ more individualistic tendencies, but the changes in the guidance from governments and the World Health Organisation (WHO) have also fueled the opposition to masks.

In March 2020, Jenny Harries, then-deputy chief medical officer for England, said it’s a “good thing” for COVID-19 patients to wear masks to protect others in their vicinity.

But for others, Harries said they tend to “contaminate the facemask and then wipe it over something” and therefore “it’s really not a good idea and doesn’t help.”

The advice is consistent with the guidance (pdf) published by the WHO during the same month, which said there had been “no evidence” a medical mask would protect people from getting sick.

The guidance said a medical mask, used correctly, can limit the spread of certain respiratory diseases, including COVID-19, but the method alone is insufficient and can “create a false sense of security that can lead to the neglect of other essential measures, such as hand hygiene practices.” It also mentioned “unnecessary costs and procurement burdens” as one of the considerations.

The guidance came at a time after Chinese buyers had purchased masks and other Personal Protective Equipment (PPE) around the globe, resulting in an acute PPE shortage worldwide.

Anthony Fauci, then-director of the U.S. National Institute of Allergy and Infectious Diseases, also advised the general population against wearing masks at the beginning of the pandemic. He later defended his recommendation at the time, telling CBS Anchor Norah O’Donnell that the advice was correct in the context of the time in which he said it as he had been told the United States had “a serious problem with the lack of PPEs.”

The UK government on June 15, 2020, mandated the wearing of face coverings in England on public transport and later in other public spaces, such as cinemas and shops. The mandate ended on Jan. 27, 2022.

According to figures revealed by London Mayor Sadiq Khan, almost 4,000 passengers were fined for breaking COVID-19 mask rules on London’s public transport.

Apart from the masking mandate, guidance to wear masks was also in place for schools, effectively meaning most students were forced to wear masks in school.

A response to a Freedom of Information request published in December last year revealed that the first time an evaluation of the masks in-class policy was provided to the Education Minister was seventeen months after schools had first been advised by the Department for Education to require children to wear masks in schools.