Nasal spray provides nearly 80 per cent protection against Covid-19, study finds
- But the antibody spray – developed by Sinovac – has side effects, and experts say more details are needed
- It was given to thousands of health workers in northern China for the study, which has yet to be peer-reviewed
Thousands of health workers were recruited for the study in Hohhot, Inner Mongolia during a Covid-19 outbreak in November. Those who used the nasal spray twice a day got infected at about one-fifth the rate of those who did not, a team of researchers reported in a paper posted to preprint server medRxiv on Saturday.
The spray was developed by Sinovac Life Sciences and contains a broad-spectrum antibody known as SA58 to neutralise the coronavirus – including all known Omicron strains, according to the company. It caused about 1,800 adverse events, such as a runny or dry nose and sneezing, during the study.
But the adverse events “were all mild and disappeared quickly without affecting daily work”, the authors from Sinovac, Peking University, the Chinese Centre for Disease Control and Prevention, Inner Mongolia Blood Centre and Inner Mongolia Fourth Hospital wrote in the paper.
“This clinical study of the SA58 nasal spray on medical personnel showed good tolerance and good effectiveness for preventing Covid-19 infections, suggesting further application in other populations in the real world,” the team said.
Their paper, which is awaiting peer review for publication, has attracted attention from around the world.
Donna Farber, an immunologist at Columbia University in New York, said the study was “interesting, but not well controlled and there isn’t enough information provided to accurately evaluate the findings”.
For instance, while the drug group was given a nasal spray containing antibodies twice a day at six-hour intervals, the control group did not receive any nasal spray.
“The proper control group would be those receiving a nasal saline spray at the same intervals without antibodies, since there could be a non-specific effect of a nasal spray on viral load or testing,” Farber said.
She noted that no information was provided on mask-wearing or other precautions taken by the two groups, or whether they took similar precautions.
Farber also said the reported adverse events from using the nasal spray “seem very high, particularly for a medication that must be taken at least twice per day to be effective”.
Nearly 30 per cent of the participants reported adverse events, according to the paper.
“That’s quite a lot for preventive medication,” Dutch medical data scientist John Jacobs wrote on Twitter.
Farber said there were already products available to deliver antibodies – proteins produced by the immune system to find and neutralise viruses – intravenously to treat severe Covid-19 cases but they were very expensive.
Applying antibodies in the nose, where the coronavirus first makes contact, would be much more effective. But Farber said controlled studies were needed to test their efficacy, such as the stability of the antibody and whether it enters blood circulation.
More than 6,600 medical personnel were recruited for the study. They were drawn from two designated Covid-19 hospitals and four “fangcang” field hospitals in the northern city of Hohhot.
The nasal spray was given to about half the participants, who were told to apply it twice a day and report any adverse events via a WeChat app. Both groups underwent PCR testing every day during the study, which ran from October 31 to November 30.
But about half the drug group dropped out during the observation period since they were no longer working at the hospitals involved, the researchers said.
Around 5,000 of the participants made it through the study. At the end of November, 135 had tested positive, including seven from the drug group and 128 from the control group.
Since those who took part were working on different shifts and rotations, the researchers converted the number of participants to a parameter called “person-days” and concluded the drug group had an infection rate of 0.026 per cent while that of the control group was 0.116 per cent.
“We recognised that the study is not a placebo-controlled, observer-blinded study and may have introduced data bias … The protective effectiveness of SA58 nasal spray remains to be verified by more clinical trials,” they wrote.
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But the best way to get antibodies against the coronavirus is through vaccination, so that the immune system can produce a high and stable concentration of them, according to Farber.
“By contrast, administration of antibodies is transient because you are only providing the antibody and there are no cellular stores to produce this antibody … It’s likely that they are very transient, necessitating repeated and daily treatments,” she said, adding that vaccines were more effective and had less side effects than antibodies in general.
