COVID nasal sprays may one day prevent and treat infection.  Here's where the science is

COVID nasal sprays may one day prevent and treat infection. Here’s where the science is

We have vaccines to boost our immune response to SARS-CoV-2, the virus that causes COVID. We have medicines you can take at home (and in the hospital) to treat COVID. Now researchers are testing something new.

They want to develop drugs that prevent the virus from entering the body in the first place. This includes nasal sprays that prevent the virus from attaching to cells in the nose.

Other researchers are studying the potential of nasal sprays to prevent the virus from replicating in the nose or to make the nose a hostile place to enter the body.

Here’s where the science stands and what we can expect next.

Read more: COVID: inhalable and nasal vaccines could offer longer lasting protection than regular injections

How could we block the virus?

“Virus blocking”, as the name suggests, is a simple premise based on blocking SARS-CoV-2. In other words, if something gets in its way, the virus can’t attach itself to a cell and it can’t infect you.

Since SARS-CoV-2 is a respiratory virus, it makes sense to administer this type of medicine where the virus primarily enters the body – through the nose, in a nasal spray.

Various groups around the world are working on this concept. Some research is still carried out in the laboratory. Some agents have progressed to preliminary human trials. None are yet available for widespread use.


Heparin is a common drug that has been used for decades to thin the blood. Studies in mice show that when heparin is given through the nose, it is safe and effective in preventing the virus from binding to cells in the nose. Researchers believe that heparin binds to the virus itself and prevents the virus from attaching to cells it tries to infect.

A clinical trial is underway in Victoria in collaboration between several Melbourne-based research centers and the University of Oxford.


Covixyl-V (ethyl lauroyl arginine hydrochloride) is another nasal spray under development. It aims to prevent COVID by blocking or modifying the cell surface to prevent the virus from becoming infected.

This compound has been explored for use in various viral infections, and early cell and small animal studies have shown that it can prevent SARS-CoV-2 attachment and reduce overall viral load.


This molecule, extracted from seaweed, acts by blocking the entry of the virus into the cells of the respiratory tract.

A study of around 400 healthcare workers suggests that a nasal spray can reduce the incidence of COVID by up to 80%.


This is a modified antibody that binds to SARS-CoV-2, preventing the virus from attaching to cells in the nose.

A nasal and oral (mouth) spray is undergoing a clinical trial to assess safety.

cold atmospheric plasma

It is a gas that contains charged particles. In cold temperatures, it can alter the surface of a cell.

A laboratory study shows that the gas alters the expression of receptors on the skin that would normally allow the virus to attach. This results in less SARS-CoV-2 attachment and infection.

Scientists now think this technology could be adapted to a nasal spray to prevent SARS-CoV-2 infection.

How could we prevent the virus from replicating?

Another tactic is to develop nasal sprays that prevent the virus from replicating in the nose.

Researchers design genetic fragments that bind to viral RNA. These fragments – called “Antisense Locked Nucleic Acid Oligonucleotides” (or ASO LNAs for short) – put a proverbial spanner in the works and prevent the virus from replicating.

A spray of these genetic fragments delivered into the nose reduced virus replication in the nose and prevented disease in small animals.

How could we change the nose?

A third strategy is to modify the environment of the nose to make it less hospitable to the virus.

This can be by using a nasal spray to change the humidity levels (with saline solution), change the pH (make the nose more acidic or alkaline), or add an anti-virus agent (iodine).

A saline solution can reduce the amount of SARS-CoV-2 in the nose by simply eliminating the virus. One study even found that saline nasal irrigation can reduce the severity of COVID disease. But we need more research on saline sprays.

A study from Australia found that an iodine-based nasal spray reduced viral load in the nose. Further clinical trials are planned.

One study used a test spray containing ingredients such as eucalyptus and clove oils, potassium chloride and glycerol. The goal was to kill the virus and change the acidity of the nose to prevent the virus from attaching itself.

This new formulation has been tested in the laboratory and in a clinical trial showing that it is safe and reduces the infection rate by approximately 34% to 13% compared to placebo controls.

Upcoming Obstacles

Despite promising data so far on nasal sprays for COVID, one of the biggest hurdles is keeping the sprays in the nose.

To overcome this, most sprays require several applications per day, sometimes every few hours.

So based on what we know so far, nasal sprays alone won’t beat COVID. But if they are found to be safe and effective in clinical trials and receive regulatory approval, they could be another tool to help prevent it.

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