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Triple threat emerging: flu, Covid, RSV
02:52 - Source: CNN

Editor’s Note: Kent Sepkowitz is a physician and infectious disease expert at Memorial Sloan Kettering Cancer Center in New York. The views expressed in this commentary are his own. Read more opinion on CNN.

CNN  — 

In the past few weeks, a new viral villain has appeared across the US: respiratory syncytial virus, or RSV. Right now, children’s hospital beds are full, classrooms are empty from RSV and similar viruses and parents are even more worried than usual.

Kent Sepkowitz

To explain this, many experts have suggested that the masking and social isolation implemented to ward off Covid-19 have created an unnaturally long period without exposure to RSV or other viruses. The result has been dubbed the “immunity gap,” a weakness in our ability to respond to the latest virus or bacteria with necessary high-precision choreography – simply due to lack of practice. It turns out that to protect ourselves from an infection, we must be exposed to it early and often.

This sort of push and pull problem where too much exposure is a pandemic and too little is a set-up for future problems, is built into the world of infectious diseases. In this world, the golden mean does not exist and equipoise is a pipe dream. The topsy-turvy problem was evident early in the pandemic and will plague us for the duration of our interactions with Covid-19 and any and all other infections.

The modern way to sidestep this problematic relationship is to substitute a fake infection – a vaccine – for actual infection. All the benefit with none of the sniffles. The problem is that we don’t yet have a vaccine available to prevent RSV and blunt the surge in cases we’re experiencing.

Of note, there is some hopeful news about protection from RSV that might be available next year for use in infants and newborns. This vaccine approach resembles the monoclonal antibodies used to treat Covid-19 and, in severely immunocompromised people, to prevent it – as opposed to conventional vaccines you might get for the flu, or the new mRNA vaccine platform for Covid-19. These injections do not enhance a person’s immune repertoire as a conventional vaccine does; rather it replaces a missing piece with synthetic antibody that can protect for weeks to months.

A more traditional vaccine is also possible for next season; this one is to be given to pregnant mothers who would make antibodies that would naturally cross across the placenta into the fetus’ bloodstream: a novel approach using traditional vaccination know-how.

The current RSV outbreak, complete with very ill children across the country, is a particularly brutal way to show, yet again, that masks and social distancing work and work well. The so-called immunity gap is nothing if not a real live incontestable demonstration of the efficacy of this sort of old school maneuver. No double-blind placebo-controlled trial is needed.

In addition to adding much grief to America’s parents, the current chaos is also sending a loud and clear message regarding the future of our ongoing struggle with Covid-19. Much peering into the crystal ball relies on our experience with influenza to model various scenarios. This makes some sense: We have a vaccine for each and an approved, though imperfect, oral antiviral.

But this vaccine is all that stands between us and an RSV-like spread of some future strain of Covid-19. To be sure, the vaccines we have against Covid-19 do a miraculous job preventing death and severe illness but have only a modest impact on the risk of catching the infection itself.

But in many important ways, RSV is a good comparator for guessing what might be next in the world of common infectious diseases (especially since there are important similarities between RSV and the coronavirus family, including SARS-CoV-2, the virus responsible for our pandemic). For all three of these respiratory illnesses – Covid-19, RSV and the flu – the evasiveness of the virus, combined with the often short-lived durability of our own antibody response combines to cause continued surges of disease.

This means that what we’re observing of RSV can help inform what we can expect from this triad of infectious diseases in the future: sickness (not just infection) every year. Some years will see more sickness than others. The group – about 20% of the US population for the Covid-19 vaccines – who decline vaccination compound the problem. A large pool without the antibody kick provided by vaccination will remain susceptible year to year. And not only will they themselves get sick but they will spread the virus to the rest of the population, new mutations and all, perpetually knocking us off balance.

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    There is some good news, though. This year’s immunity-gap-based rise in RSV cases is clear evidence that the best way to handle SARS-CoV-2 is not a fleet of better vaccines and stronger antivirals, but rather wearing masks and avoiding crowded indoor rooms. Today’s RSV crisis is tomorrow’s path forward. In other words, in the “too much exposure, too little exposure” problem, it is always best to prevent now and worry later. There is no other choice to make, as the death of more than a million Americans from Covid-19 demonstrates.

    So what does this mean for your upcoming Thanksgiving dinner? Does everyone need to sit 6 feet apart and slip bites of turkey under a mask? Although I don’t know what the official recommendations will be, here is what I will be doing: When I take a subway or bus to the grocery store, I will wear a mask. When I am in the store, I will wear a mask. When I walk around the city from place to place I will remove the mask and enjoy the cool air. And, other than insist on vaccinated attendees only and imploring family members to stay home if they are feeling ill, I will enjoy my Thanksgiving dinner at a crowded dining room table, 100% mask-free.

    I hope I am right.