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Dr Dominik Mertz, associate professor in the Division of Infectious Diseases at McMaster University and medical director of infection prevention and control at Hamilton Health Sciences, joins Dr Roman Jaeschke to discuss the current coronavirus disease 2019 (COVID-19) situation, prevention, and treatment options in Ontario.
Roman Jaeschke, MD, MSc: Good afternoon, welcome to another edition of McMaster Perspective. I would like to introduce Professor Dominik Mertz, who is the director of Infectious Diseases division in the Department of Medicine at McMaster University. What I would like to talk about is something we are all struggling with, which is changing ideas, changing recommendations, and changing patterns of using masks. I will phrase my question carefully—I will not ask what we have to do [about that], but I will ask: what is your opinion, Professor Mertz, about what we should do these days?
Dominik Mertz, MD, MSc: The overarching advice I always make is [to] follow the public health requirements. So, first of all, make sure that you comply with what the government or public health [authority] asks you to do. Now, the opinions whether that’s the right or wrong approach vary a lot; [there are] people out there who would say, “[Wear] masks every time, any time, regardless of epidemiology,” etc, and yet you have others who would say, “Masks don’t work at all. There’s never a role for them.” And in my mind, the truth is somewhere in between, which makes it, from a policy position perspective, such a difficult topic, right? Because (a) it’s been politicized, (b) there are very strong opinions out there. And then, navigating through that, you never make everyone happy. I think that’s what we’ve been seeing. For me personally, I think in the current situation having a recommendation to mask for those who want to mask makes absolutely sense in health care. With patient contact, I’m fully supportive of the mandate at this point, acknowledging that many European countries have stopped [using masks] in health care as well, and they seem to be doing okay from an outbreak perspective. So to me, there’s still a lot of uncertainty there [as to] what the way forward will be. But I think, again, the current approach where we treat highest-risk settings differently than the public at large makes sense.
Roman Jaeschke: So, these would be health-care facilities like hospitals, but also long-term facilities with a lot of elderly, theoretically vulnerable, people. If I hear correctly, you would be on the side of recommending a graded approach, depending on your risk of acquiring it due to your personal characteristics as well as social characteristics of the milieu you are operating in. Would that be fair at the moment?
Dominik Mertz: The milieu and the epidemiologic situation at large. So, the most benefit from any intervention you get is when there’s a huge COVID-19 pressure out there, while there’s a minimal effect when there’s little pressure or few incidents, and I think that needs to be taken into consideration as well and should also result in sort of a graded level of recommendation, in my mind.
Roman Jaeschke: Maybe we can then talk about what’s currently happening in Canada or even in Ontario, because all those recommendations are made in the setting of epidemiological pressure. Where are we these days? It’s July 7th [2022], by the way.
Dominik Mertz: By July 7th we are past an odd year from the last Omicron wave. We see things picking up again, the BA.5 [variant] taking over, similar to what we’ve seen happening before in many European countries as well. The big question at this point is how far up this will go in a setting where (a) it’s summer, which comes to our benefit with more outdoor than indoor activities and so on. It’s not the preferred season, I would say, for COVID-19, but nevertheless, obviously it can spread, (b) we do have—nonperfect, but we still have—a lot of population immunity from having gone through 2 quite major Omicron waves, so that should help us. But the BA.5 will be more easily transmittable, first and foremost, because of the level of immune escape it has —despite the fact that we have a lot of vaccine immunity, we have a lot of additional immunity from recent infections from Omicron. And that’s what we see now results in an increase in numbers, and it is to be determined how things will look like in a month or two from now, whether it will be something that only happens through summer and then goes back down, or whether this is sort of the start that will continue to build up into fall and winter.
Roman Jaeschke: And what do we know about the severity of BA.5 [infection]?
Dominik Mertz: To the best of my knowledge, similar to the other Omicrons, it looks from those countries that already went through the BA.5 wave that in general they saw even fewer hospitalizations than they would have expected. But that is probably not because of BA.5 being milder than the previous Omicrons. It’s just because there’s more immunity in the population than half a year ago, so probably similar. I think that’s the bottom line, in my mind.
Roman Jaeschke: Could it also be that we have some outpatient treatment these days that may prevent some admissions—critical care admissions—and deaths? Again, different places will have different rules, but how do we deal with outpatient treatment of vulnerable people with COVID-19 in Ontario?
Dominik Mertz: As you mentioned, it’s different from jurisdiction to jurisdiction. In the Ontario setting pretty much everyone who can prescribe can prescribe Paxlovid, and it’s available in the local pharmacies, and the pharmacists make also sure that in terms of interactions, which are the main challenge with Paxlovid, it is safe to use or whether any of the other medications need to be changed. So, that’s the process. Then we have different recommended criteria from the province, which are a little bit more lenient than the Science Table recommendations, which are a little bit more strict. There you would go by age, vaccine status, and number of comorbidities and based on that you need to have an indication for Paxlovid or not. All of this being said, the data behind all of that are very indirect and we don’t really understand very well at this point how much Paxlovid adds in a vaccinated individual. Highest risk, unvaccinated—no question. We do have the data, which show very high efficacy of this treatment in preventing severe infection, in preventing death. We don’t have the same data for lower-risk individuals or standard-risk individuals that include many of us who are vaccinated, may have one or the other comorbidity. So we don’t really know how much it adds in those situations, which makes it often sort of a judgment call what you do. But I think at this point, following those criteria based on the risk profile, based on this Science Table [data], an estimate of a ≥5% risk of hospital admissions would result in an indication for Paxlovid. It’s probably a reasonable approach: sort of accepting that uncertainty that we have, but at the same time erring on the side of caution of probably overprescribing at this point.
Roman Jaeschke: What are the downsides of Paxlovid? Without knowing I could think of side effects, I could think about cost, I could think about drug interactions. What are they? Why are we hesitant to give it, say, as a prevention or in the mildest disease but not highest risk?
Dominik Mertz: The hesitancy stems from the fact that you haven’t a proven effect in that population, right? So that’s one piece. And when we think about low-risk individuals, we don’t have any data that would support that benefit to start with. The main challenge or drawback, if you think about using it more leniently at this point, is mostly the interactions, which can be challenging. Again, you can argue that in a young, healthy individual you could easily prescribe Paxlovid because they are usually not on other drugs, but those are the ones that, to the best of our knowledge, don’t benefit from the treatment. And in the elderly population with comorbidities, where you have more likely or likely more significant effect, that’s where you have all those other medications in the system. And that’s usually the main challenge. From a side-effect perspective, it’s a well-tolerated drug, so that’s less of an issue.
Roman Jaeschke: Thank you very much for this update as of today, as of the beginning of July [2022]. We’ll see how the situation evolves. I hope we will not have to talk in a week or two because it would mean some dramatic changes, but I’m already inviting you for an update, say, in another month. Thank you very much, Professor Mertz, I really appreciate it and I appreciate your work on probably 20 chapters in the McMaster Textbook of Internal Medicine. You are one of our star authors. Thank you.
Dominik Mertz: Thank you, Roman.
Roman Jaeschke: Goodbye.
Dominik Mertz: Okay, thanks. Bye-bye.
