What can we anticipate from the coronavirus in the upcoming fall season?

 

Throughout the United States, a growing number of COVID-19 patients are being admitted to hospitals each week, marking a clear indication that overall case numbers are on the rise.

Data from the U.S. Centers for Disease Control and Prevention reveals an increase in detectable coronavirus levels in wastewater samples and a rise in the percentage of positive test results since June. Although indirect, both of these metrics point to a surge in cases at the national level. However, it has become challenging to precisely gauge the emergence of new outbreaks or comprehend the situation within various communities. This is partly due to the fact that states are no longer obligated to report new cases, a consequence of the conclusion of the U.S. public health emergency in May (as reported on May 4, 2023).

We are aware that the most severe phase of the pandemic is largely in the past. While the virus is still capable of spreading and continues to do so, its transmission is not as overwhelming as it was during the initial years of the pandemic.

In the midst of an evolving landscape of variants, including a new iteration of the omicron variant labeled BA.2.86 that is closely monitored by global and U.S. health agencies, the majority of infections now tend to be less lethal compared to the early stages of the pandemic. According to data from blood banks, as of September 2022, approximately 96 percent of individuals in the United States have received vaccination, contracted the virus, or encountered both, which can contribute to mitigating the severity of subsequent infections. Additionally, a new booster shot, developed to target relatives of a viral lineage referred to as XBB, is anticipated to become available by the end of September (as reported on January 13, 2023).

Despite these glimmers of optimism, our trajectory with SARS-CoV-2, the virus responsible for COVID, remains uncertain. The virus is here to stay; new variants will persist, displaying varying levels of transmissibility and severity. How many individuals might experience illness or loss of life on an annual basis? That remains an unknown.

To address this inquiry, the virus must have transitioned into its endemic phase, characterized by consistent circulation at a certain baseline level. However, even in an endemic state, the virus does not become benign. During this phase, individuals will still contract COVID, and some cases will be severe. Yet, the number of hospitalizations and deaths in a "typical" year will be significantly lower than during the pandemic years.

In an attempt to gauge if the forthcoming autumn—marking our fourth season with COVID and the first without an ongoing public health emergency—could potentially mark the initiation of the virus's endemic phase, Science News engaged in a discussion with epidemiologist Aubree Gordon from the University of Michigan in Ann Arbor. The conversation has been edited for conciseness and clarity.

SN: How does this fall differ from previous years?

Gordon: One of the significant differences this fall is that, at this juncture, nearly everyone possesses some form of immunity against SARS-CoV-2.

The majority of individuals have acquired hybrid immunity, indicating that a substantial portion of the population in the United States has not only received vaccinations but has also experienced an infection. A significant proportion of those who opted not to receive vaccinations have encountered infections on multiple occasions. Similarly, some individuals who were vaccinated have also experienced recurrent infections.

Consequently, we now possess a heightened level of immunity against the virus. While this immunity doesn't entirely prevent individuals from getting infected or reinfected, it undoubtedly contributes to diminishing the severity of these infections when they do occur.

SN: What insights have we gained regarding the characteristics of reinfections?

Gordon: Generally, reinfections tend to be considerably less severe compared to initial infections. However, instances of severe reinfections are still observed. When we discuss severity, we encompass not only fatal infections, which are undoubtedly the most serious, but also infections that necessitate hospitalization or might lead to persistent symptoms in the long term.

SN: A new booster is set to replace the omicron variant this fall. How crucial is it to receive this booster?

Gordon: I believe that booster shots are definitely recommended, particularly for individuals who are at a higher risk of experiencing severe illness. I had sincerely hoped that we would have reached a stage where SARS-CoV-2 resembled a seasonal coronavirus, causing symptoms akin to a common cold, and thus being less severe than influenza. However, what we continue to observe with SARS-CoV-2 is that its severity surpasses that of the flu. It is still responsible for a considerably higher number of annual deaths compared to the flu. It's uncertain whether we have truly reached the state of being fully endemic, where transmission stabilizes within an average range from year to year.

SN: In your opinion, where do you think we currently stand on the spectrum between pandemic and endemic?

Gordon: I believe we are approaching the threshold of what an endemic state will resemble. However, I'm uncertain whether we will have fully reached that state in the upcoming season, or if it might take another season or two for us to achieve it. I will mention that I'm somewhat hopeful that we haven't reached the endemic level just yet, at least based on last year's data. This is because there were a considerable number of deaths in the United States, estimated at 244,000 by the CDC. This figure is four to five times higher than the mortality seen in a severe seasonal influenza season in the United States. However, the severity of COVID-19 has been on a decline over the past several months. The hope is that this downward trajectory in severe and fatal cases will continue. If COVID-19 had transitioned to its endemic stage, we would anticipate observing fluctuations from season to season, but these fluctuations would center around a consistent number rather than perpetuating a downward trend towards reduced severity.

SN: Over the past year, have researchers gained any insights into what an endemic phase might entail?

Gordon: I believe we are honing in on the characteristics of an endemic state. It has become increasingly evident that this will be a recurring infection that individuals might experience more frequently than the flu. There's a possibility that the virus's rate of mutation may decrease. For adults, who are more susceptible to severe illness compared to children, it seems likely that the virus's danger level will be on par with, if not greater than, influenza. However, this is still a matter that requires further examination. Initially, I had thought that everyone might need a vaccination along with one or two infections to reach the endemic stage. However, it's possible that achieving the endemic state requires a slightly broader form of immunity, which can safeguard against a wider range of virus variants, as well as more instances of exposure.

SN: In your opinion, what insights do you think experts might gain during this fall?

Gordon: This fall, one aspect we'll be closely observing is how it differs from the previous fall. If we continue to witness a decline in cases, it might indicate that we haven't yet reached the endemic state. Alternatively, if we observe a pattern similar to the past fall, it could suggest that we have indeed entered the endemic phase. Season-to-season variations, as well as the emergence of new variants, will contribute to the severity of the SARS-CoV-2 season on an annual basis. This variability is comparable to what we observe with the flu. For recent flu seasons (excluding pandemic years), the CDC estimates ranged from 12,000 to 52,000 deaths per year. Such substantial variability is inherent in the nature of these diseases.