COVID-19
Experts worry that the Ministry of Health’s internal and public health advice is not in line with the latest science, Marc Daalder reports
Health Ministry officials advised the government to distribute less effective surgical masks to vulnerable communities because they feared people would become complacent if they were given highly effective N95 respirators.
This is one of the few recent decisions that experts say don’t fully reflect the latest science on Covid-19. The ministry has been urged to provide clearer advice on both the use of masks and what a positive RAT result means at the end of the isolation period of a Covid-19 case.
Better masks could affect compliance, MoH . advised
The advice on masks came at the end of April during a briefing to then Covid-19 minister Chris Hipkins and current Covid-19 minister Ayesha Verrall. In the briefing, released under the Official Information Act, officials provided three types of masks to be given to “clinically vulnerable and high-risk populations.”
Those include the gold standard N95 or P2 respirators, alternative respirators such as the Chinese KN95 or Korean KF94 which are almost as good, and typical surgical masks.
Officials admitted that “P2/N95 respirators … probably provide the highest level of respiratory protection of the three options considered. It is estimated that the appropriate filtration efficiency of such a respirator is up to 98 percent, compared to about 38.5 percent for a [surgical mask]†
At a population level, however, the Department of Health thought that surgical masks “would likely be more effective than dust masks in reducing transmission of Covid-19 (and other respiratory diseases), serious illness and death”.
That’s because they were concerned that people wouldn’t know how to properly wear a gas mask and because “a possible perception by some individuals that they are ‘protected’ by a higher quality mask can increase complacency and increase compliance.” of basic infection prevention and control practices: The benefits of increased respiratory protection may be offset by reduced adherence to basic practices, such as staying home when sick, physical distancing, or washing hands.”
Amanda Kvalsvig, an epidemiologist at the University of Otago and one of the first advocates for the use of masks in New Zealand during the pandemic, said there was no reason to believe that respirators would be less effective at the population level than surgical masks. .
“The two main factors that determine the effectiveness of the mask are the filtration efficiency (how good the mask is at filtering out particles, in this case viruses) and the quality of the fit (how well the mask fits on the face). masks are clearly much more effective virus filters than medical masks,” she said.
“For population-level effectiveness you have to add one more factor, broad coverage. The more people who wear masks, the better the system works because then you have two-way protection: source control (people wearing masks breathe less virus in the air around them) and respiratory protection (people who wear masks breathe less viruses) You can see that this system works better both ways when people wear good quality masks.
“There is no basis for recommending New Zealanders wear less effective masks in the hopes that this would make them more concerned about Covid infection and more likely to take other precautions. The evidence does not support this approach at all. “
A study in Scientific reports of earlier this year said there was no evidence that people who wear masks are less likely to follow other health advice.
A spokesman defended the ministry’s position that more effective masks could reduce compliance with other measures.
“This comment was part of a discussion about the true efficacy of PPE and is a valid concern based on observations of individuals’ behaviour. The Department of Health conducts regular behavioral insights studies to address mask-wearing issues. to grab.”
This is only the last time the Ministry behind the ball has been found on masks. In December 2020, Director General of Health Ashley Bloomfield told Cabinet mask mandates on public transport should be revoked after summer. A draft paper prepared for Bloomfield in February 2021 similarly recommended repealing the obligation to wear masks on public transport.
RAT result debate
Another request from the Civil Service Act has raised further concerns about the evidence base for the ministry’s advice.
As recently as Maysaid official advice that Covid-19 cases that return a positive RAT test after seven days of isolation are not contagious.
“If you’ve taken a RAT, the result would probably be positive, but that doesn’t mean you’re contagious,” the government’s Covid-19 website read in May.
When requested in an OIA request to provide the evidence behind these statements, the Department of Health responded with a series of links that did not answer the question.
That’s because, experts say, the ministry is wrong. RAT results correlate very closely with infectivity in the late stages of an infection. And between 12 and 25 percent of Covid-19 cases are still contagious after seven days – so a week is a good rule of thumb, but won’t suit everyone.
“Between 30 and 60 percent of people who test positive for a rapid antigen test are still contagious after that seven-day period. And of those who aren’t still contagious but did test positive, they were still contagious yesterday,” Emily Harvey, the co-lead of the Contagion Network modeling program at Covid-19 Modeling Aotearoa told Newsroom.
In other words, even after seven days of isolation, a positive test result could mean you’re still contagious. That’s why experts like Harvey have advocated a test-to-release policy, where isolation ends as soon as you test negative, rather than the seven-day isolation period.
“If you shorten the minimum isolation period but require test-to-release — especially two negatives in a row — you can shorten the average isolation period without increasing the further risk,” Harvey said.
This would allow more people to get out of their isolation faster, while preventing others from infecting people because they were still contagious after seven days.
“The latest evidence on testing methods and strategies to limit transmission of Covid-19, including the isolation periods, is evolving rapidly,” the ministry spokesman said, when asked if changes to the isolation advice were being considered.
“We continue to review and evaluate data regularly to inform our approach to testing and isolation. Any change must ensure a balance between effective outbreak control, minimizing the impact on vulnerable communities and the health system, and the effects isolation/quarantine has on the wider society.”
New advice, communication needed
Even setting aside specific policy changes, both Kvalsvig and Harvey say health communications that are closer to science are critical.
“I would like the Department of Health to send a very clear message about how strongly the evidence supports a protective effect of masks. I would like them to be clear to the public about the challenges we are facing this winter and the important role of wearing masks to dampen the spread of Covid, flu and many other infections,” Kvalsvig said.
“Often, government communications about masks during the pandemic seem to indicate that people who want to wear masks are overprotective. That’s very problematic public health messaging for all sorts of reasons. None of us want to be the one to see a beloved friend or family member become seriously ill, and wearing a mask can be an important protection for those around us.”
For Harvey, better communication seems like a clearer explanation of what a positive test result means after seven days and advice to take extra precautions for a few days, even after those seven days are up.
“I don’t think the message got through that these antigen tests actually detect a live virus. They won’t test positive for a day or two after you’re no longer contagious,” she said.
“Some of the previous posts about not worrying about positive tests have been removed, but no strong action has been taken against them. The revisions have not been clearly communicated to the general public.”
Ministry web pages currently only advise people not to take a test after seven days of isolation. But the Health Ministry spokesman said the evidence for the interpretation of a positive RAT result was still mixed.
“The Department of Health recognizes that a small number of people will remain contagious for more than seven days after they have a positive RAT result, but as time goes on and a person recovers, a positive RAT is less likely to indicate contagiousness” the spokesperson said. said.
“The evidence to date on what a RAT result at the end of a seven-day isolation period can tell us about infectivity is difficult to interpret… For these reasons, we do not recommend routine testing at day seven, as this does not the case. a reliable process.”