Study Suggests Air Filters Ineffective Against COVID and Other Respiratory Infections; Some Experts Disagree

Air filters flew off the shelves during the pandemic, but research questioned their efficacy in preventing infections. One expert has a different take.

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Once heralded as our guardians against COVID’s airborne onslaught, airflow defenders may have fallen from grace.

During the COVID pandemic, public health authorities promoted three types of air filters to prevent airborne transmission of the virus. These included high-efficiency particulate air (HEPA) filters to remove viruses from the air; ultraviolet (UV) filters using high-frequency light to deactivate airborne viruses; and ionizers that electrically charge particles so they settle on surfaces rather than float freely.

A scientific review analyzed the worldwide evidence and concluded that the trio of air filters offers little protection against respiratory and gastrointestinal infections. However, it turns out that the review itself has come under scrutiny.

Air Filters Found Ineffective in ‘Real World Settings’

A new systematic review of global observational and experimental studies conducted between 1970 and 2022 analyzing indoor air treatment for preventing infections was just published in Preventive Medicine. Researchers analyzed infection rates and symptoms of people exposed to air purification in indoor public spaces for a minimum of 20 hours weekly.

After pooling data from 32 studies, they found no conclusive advantage to the air filtration methods examined in reducing symptom severity or frequency without confirmed infection.

Although they did find lower infection incidence in a few cohort studies examining HEPA filtration and ionizers, results varied across study designs.

While environmental and surface contamination does decrease after treatments like UV light and HEPA filters, there is limited “robust evidence” that these effectively reduce respiratory or gastrointestinal infections.

Lead researcher Julii Brainard, who holds a doctorate in environmental sciences and is from the University of East Anglia’s Norwich Medical School, told The Epoch Times that air treatment methods to prevent gastrointestinal or respiratory infections and symptoms shouldn’t be relied upon.

She noted that there are “many more” effective things we can do instead to prevent illness— especially severe illness—from infections.

“Vaccination tops that list of alternatives,” she said. “Social distancing, especially when newly ill, can also prevent infections.” Although, she admitted, social distancing can be difficult to maintain.

Ms. Brainard emphasized that air treatment methods can only slow down an epidemic but won’t stop it.

“This is why vaccination is wonderful,” she continued. “Vaccination can stop an epidemic and infection spread and prevent severe illness like nothing else can.”

Study Limited by Its Design, More Work Is Needed

According to Ms. Brainard, the main limitation of this research is that the study design allowed the research team only to summarize the available studies, meaning that none of the research is “new” information.

“That’s why we repeatedly state that it will be good to see results of experiments started in last 2 to 3 years, to see if the results are consistent given that air treatment methods are developing all the time,” she explained via email, pointing out that how recently the data were published matters, especially with a technological idea like air treatment.

“We can’t rule out that some new technology will have different results, or that studies describing larger populations will reveal a real, but rarer or very small if consistent effect,” Ms. Brainard continued, adding that there are good reasons to think that the newer research won’t be any more supportive of air treatment methods to prevent respiratory infections.

According to Ms. Brainard, the odds are high that most infection transmissions are immediate, and air treatment methods simply cannot decontaminate air fast enough before most transmissions happen. Also, since most transmissions are likely to occur at short distances and air filters don’t stop people from standing close to each other, air filters don’t address the key thing (proximity) required to prevent transmission.

“I haven’t seen a review publishing how physically close people were standing at point of likely transmission; how would someone even collect that information reliably?” she asked. “But in a relative sense, we know that proximity matters hugely to transmission risk, [which] is why during pandemic people were advised to stand 6 feet or 2 meters away from each other,” she wrote.

Research Seriously Flawed: Expert

The review fails to specifically address COVID, instead covering respiratory and gastrointestinal infections generally, Dr. Jacob Teitelbaum, a board-certified internist, author, and director of the Practitioners Alliance Network, told The Epoch Times. “It is a horrible study and does not supply much in the way of useful clinical information.”

Dr. Teitelbaum said what the study does suggest is that HEPA filtration can decrease the risk of getting infections.

While suggesting HEPA filtration may reduce infection risk overall, Dr. Teitelbaum noted that one can’t base clinical decisions on this “hopelessly flawed” study. Participants only spent about 15 percent of their day in filtered spaces, leaving ample infection exposure the rest of the day.

Additionally, he found the researchers’ decision to count basic air conditioning—which, if not properly cleaned, can spread contaminants—as a filtration system “absurd.” The researchers also compared filtration to simply opening windows—already proven to control airborne infection.

Measures like opening windows explain how massive rallies with shoulder-to-shoulder people can occur without a spike in COVID cases, according to Dr. Teitelbaum. It’s because these gatherings happen outdoors.

“In a field full of useless studies on COVID, I find this to be a shining example of yet another,” he said.

What Truly Protects Against Infection Spread?

“Remember that in most households, if somebody gets COVID, only 1 in 6 members of the household will also get it from them,” Dr. Teitelbaum said. “Which means that our own immunity is critical.”

To bolster immunity, he recommends the following:

• Taking a quality multivitamin rich in zinc, vitamin C, and other immune-boosting nutrients.
• Staying hydrated with non-sugary fluids, “although adding a teaspoon or two of sugar to coffee or tea is okay.”
• Getting at least eight hours of sleep nightly to refresh the immune system.

“These simple measures dramatically improved immunity, which can decrease COVID risk,” Dr. Teitelbaum said. He also recommended elderberry extracts and similar botanicals to minimize viral respiratory risks overall.

The Greatest Risk Has Already Passed

Since most people now have some exposure to the virus, the pandemic’s peak infection risk has passed, Dr. Teitelbaum said.

With novel viruses, the first outbreak tends to be the most severe, much like the devastating introduction of measles to the Americas and Hawaii, he added. “We are now largely past that,” he noted. As population immunity grows, COVID-19 has become one more manageable infectious threat among many with which we coexist.

“It warrants common sense but not fear,” Dr. Teitelbaum said. “Chronic fear is toxic. I invite people to choose common sense instead.”

The Epoch Times has reached out to the study’s lead researcher, Ms. Brainard, for comment.

Views expressed in this article are the opinions of the author and do not necessarily reflect the views of The Epoch Times. Epoch Health welcomes professional discussion and friendly debate. To submit an opinion piece, please follow these guidelines and submit through our form here.