Will COVID-19 Become a Seasonal Illness? Here’s What We Know Right Now

• New research suggests that COVID-19 could develop into a seasonal illness once herd immunity is achieved.
• Some experts, however, say herd immunity may be difficult to obtain.
• They say a vaccine is the best way to achieve community-wide immunity.
• They also note it’s important to develop treatments for COVID-19 as well as a vaccine to help prevent it.

Dr. Howard Forman has been working in the public health arena for 22 years.

Forman is a professor at Yale University in Connecticut who teaches public health. He also runs Yale’s Healthcare Curriculum and has worked as a health policy fellow in the U.S. Senate.

But he’s never seen anything quite like COVID-19.

Tracking the data during this pandemic, Forman said scientists are still learning about how this vexing virus works.

“We know very little,” said Forman, who’s also a practicing emergency/trauma radiologist.

“We need to absorb as much as we can and make the best decisions using this information,” he told Healthline. “We will learn many lessons from this outbreak and should not be foolish enough to think we have all the answers now.”

Will COVID-19 become seasonal?

Case in point is a new COVID-19 research review published today in the journal Frontiers in Public Health.

The review suggests that COVID-19 will likely become seasonal in countries with temperate climates.

However, researchers note that this will happen only after herd immunity is achieved — which might take years.

Until that time, COVID-19 will continue to circulate across the seasons, the authors state.

Dr. Hassan Zaraket, an assistant professor at the American University of Beirut in Lebanon and a senior author of the study, said that these conclusions highlight the importance of public health measures to control the virus.

The authors state: “The public will need to learn to live with it and continue practicing the best prevention measures, including wearing of masks, physical distancing, hand hygiene, and avoidance of gatherings.”

Challenging the findings

Forman challenges the conclusions of the review, which were submitted in May and published today.

“I think that the authors wrote and opined at a difficult time. We have seen almost no unmitigated outbreaks,” Forman said.

“So, did Brazil start to get better because winter had started? Or because they took actions? Is India getting worse because it is hot or because summer is waning? The outbreaks in Italy and Spain suggest that bad outbreaks can begin during the worst part of winter and also during the peak of summer,” he said.

“I think we need more time and more data to make conclusions about this particular coronavirus,” Forman added.

Things clearly change quickly with COVID-19 as scientists learn more.

“I think we all need to be humble,” Forman said. “I was in medical school when the AIDS crisis began. I am the sibling of a survivor of congenital rubella. Infectious diseases have shaped my life in these and other ways.”

Study author responds

“I agree with Dr. Forman that this is still an ongoing pandemic,” Zaraket told Healthline. “Thus, even though we learned a lot about SARS-CoV-2 and its disease, a lot of unknowns still exist.”

Zaraket also agreed that the climate currently seems to be “playing a minimal role in SARS-CoV-2 circulation as evident by the second wave of disease that countries are dealing with in the Northern Hemisphere despite summer. This, we attribute to the fact that the population remains susceptible at large to the virus, which can easily spread, overcoming climate conditions.”

But Zaraket added that scientists do agree that herd immunity will reduce transmission of the virus, “and this, we suggest, will make the disease more prone to seasonal changes.”

Although SARS-CoV-2 is a new strain, Zaraket said, “It shares similar properties with other common cold coronaviruses, including the HKU1 strain which belongs to the same lineage — beta coronaviruses.”

“The reasons we believe that SARS-CoV-2 will continue to circulate even after herd immunity is developed include the propensity of the virus to mutate and evade immunity,” he added. “Vaccines will not be 100 percent effective, the immunity will wane over time, and reinfections, while still rare, do occur.”

In fact, he continued, “reinfections have been shown to occur frequently with other seasonal coronavirus strains.”

Zaraket explained that the journal article “is not primary research but is a review paper based on what is known” regarding the seasonality of respiratory viruses and the properties of SARS-CoV-2 and COVID-19.

He said the virus will become seasonal, “but only after herd immunity has been achieved, which is expected to reduce the transmission rate of the virus.”

Zaraket said the Food and Drug Administration expects a COVID-19 vaccine to protect at least 50 percent of vaccinated people from an infection or severe disease.

“Thus, we might have vaccines that have moderate effectiveness being approved, but they would still help mitigate the pandemic,” Zaraket said.

Will the virus prevail in winter?

Dr. Robert Turner Schooley, an infectious disease specialist and professor of medicine at the University of California in San Diego, predicts the virus will likely be more prevalent in winter.

He told Healthline there are two reasons for this.

“First, as people move indoors, it is highly likely that there will be more unmasked human contact in settings in which the virus can pass from human to human in settings where aerosols accumulate,” Schooley said.

“Second, as aerosol scientists will tell you, aerosols and droplets dry much more rapidly in low humidity conditions such as those found indoors in rooms that are heated,” he noted.

“When moisture is wicked from aerosols, the individual particles become lighter and they persist in the air for longer periods of time, providing them with more time to pass from person to person,” he said.

Schooley explained that “seasonality” will become more evident when there is enough immunity in the community to substantially reduce transmission in conditions of less intense exposure.

“With the extremely low levels of immunity at present, the virus easily finds people without immunity to infect under summer conditions,” he said.

Another factor to consider, Schooley said, is that immunity to this virus wanes rapidly and increasing reports of reinfection are appearing as the first wave of infections from the spring of 2020 get further behind us.

“This virus is, thus, behaving like each of the other three common coronaviruses that have been present in the human population for several hundred years or more,” he said.

“As immunity from prior infections wane, individuals become more susceptible to reinfection,” he said. “When enough people in the population become sufficiently susceptible, a new wave of infections sweeps through the population.”

Schooley explained that other coronaviruses such as the OC43 and 229 strains cause “relatively trivial disease” and the human population sees waves sweep through a large fraction of the population during each 3- to 4-year cycle.

Immunity of the population as a whole is effectively reinforced with each wave.

Just what immunization will do to modify infection rates depends on the effectiveness of the vaccines brought into the human population both from the perspective of shorter term and longer term effectiveness, Schooley said.

“We’ve seen natural immunity wane rapidly enough for people to be reinfected within months. There is little reason to believe anything but that our first generations of vaccines will be more effective than natural infection in inducing strong and durable immunity,” he said.

For the foreseeable future, Schooley predicted: “We are going to need to be aware that this virus will be lurking over our shoulders, and we will very likely need to use masks, social distancing, and other measures to prevent outbreaks and recrudescence as we are now seeing in Europe and other parts of the world as people return to pre-SARS-CoV-2 levels of interaction.”

What is herd immunity?

Forman said that while scientists differ, it’s important to have open discussions, especially when it comes to misunderstood issues such as herd immunity.

It’s a term that gets thrown around a lot these days. But what exactly is herd immunity?

It’s what occurs when a large enough percentage of people in a community become immune to an infectious disease that it stops the disease from spreading.

This can only happen through widespread vaccination against the disease, or when many people contract the disease and in time build up an immunity to it.

Herd immunity is supported by some experts in the scientific fields.

Scott W. Atlas, a senior fellow at Stanford University’s Hoover Institution and a former Stanford University Medical Center chief of neuroradiology, is one of President Trump’s newest medical advisors.

He has reportedly embraced herd immunity as a strategy to fight the pandemic.

Atlas and the White House have denied that they support herd immunity, but he reportedly told Fox News in June that “misinformation has spread” about herd immunity.

“The reality is that when a population has enough people who have had the infection, and since these people don’t have a problem with the infection, that’s not a problem. That’s not a bad thing,” he said.

Then in July, Atlas told Fox News Radio: “When you isolate everyone, including all the healthy people, you’re prolonging the problem because you’re preventing population immunity. Low-risk groups getting the infection is not a problem. In fact, it’s a positive.”

Atlas reportedly wanted the United States to do essentially what Sweden did, which was not ordering any lockdowns or closing many schools and businesses.

But Sweden’s effort to attain herd immunity failed. Sweden is now among the world’s most infected countries per capita.

Most scientists interviewed for this story agreed that pursuing herd immunity in the United States would have allowed the virus to transmit to most of the population, and hundreds of thousands and perhaps millions would have died.

Treatments are needed, too

Schooley told Healthline that safe and effective drugs may also have an impact on this virus.

“Significant progress is being made on the drug front,” he said. “And it should be remembered that it is a combination of drug therapy and behavioral changes that has converted HIV from a disease we knew in the early and mid-1980s, to the present when it is reasonably well contained in places where access to antiretroviral therapy is unimpeded.”

Schooley added that long-acting and orally bioavailable drugs “could well have a major impact on the epidemiology and the morbidity and mortality of SARS-CoV-2, and we should invest in their development just as passionately as we are in vaccines.”

But vaccines and drugs aren’t the same thing.

Vaccines are given to people who haven’t had an illness in an effort to induce an immune response to a pathogen — bacterium, virus, or parasite — so that they’re less likely to contract it or become ill if they are exposed to the infectious agent in question.

Drugs are generally given to people who already have an illness or a virus to help them recover.

“There are rare exceptions,” Schooley said. “Some drugs, such as antibiotics, are used to prevent infections, but this is much less common than giving them to treat people who are already infected.”

In the case of HIV, Schooley concluded, “we do not have any effective vaccines, but we do have drugs that we use to prevent infection. The same might ultimately be true for SARS-CoV-2 if vaccine development stalls.”

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