San Francisco Chronicle - (Sunday)
COVID will still be with us for years
Unique features of the coronavirus make it unlikely to be eradicated
How will COVID-19 impact your life next year, in 2025 or in a decade? Will you be masked in perpetuity? Will a vaccineresistant variant emerge that sets the world back to square one?
To fully understand COVID-19 and its long-term implications for our society, it is important to first understand some key definitions in infectious diseases epidemiology.
An epidemic is an infectious outbreak that causes disease within a large number of people in one region. A pandemic, meanwhile, is the spread of that disease to multiple countries or continents across the world.
In the history of epidemiology, experts have never counted individuals without symptoms into these definitions. A “case” was previously defined as a symptomatic person who displayed signs of illness stemming from a pathogen. The virus that causes COVID-19 changed all that, however, due to its potential for viral transmission even when a person has no symptoms.
Massive testing across the planet, therefore, became necessary to try to interrupt chains of transmission. But testing cannot identify every asymptomatic person. Nor do we accurately document all symptomatic coronavirus infections, since mild or moderate symptoms can resemble those of other respiratory viruses like the flu. This leaves us in the position of counting all positive tests (whether a patient is ill or not) as cases. We mainly track COVID-19 by documenting the prevalence of severe disease as manifested by hospitalizations.
An epidemic of COVID-19 in the Bay Area becomes endemic when the disease is manageable locally (e.g., not causing an undue burden of hospitalizations or health care utilization) but is not likely to be eliminated due to inherent properties of the pathogen. Elimination means reducing the symptomatic incidence of disease in a certain geographical region to zero.
Eradication, meanwhile, means reducing the incidence of the disease worldwide to zero. Inherent properties of a pathogen that make it eradicable include the inability to be hosted in animals, clear signs and symptoms that are distinctive to the pathogen (e.g., the distinctive skin eruptions or pox of the smallpox virus) so it can be recognized and contained, a short period of infectiousness, acquisition of natural immunity for life and, eventually, a highly effective vaccine.
Only rinderpest (a disease of cattle) and smallpox have been successfully eradicated from the planet.
Most serious infections we encounter can't be eradicated but can be controlled by ongoing vaccination or treatment. Controlling a disease means it becomes endemic after being brought to low circulation levels and impact.
Measles, a highly transmissible respiratory virus, is likely not eradicable but does lead to high levels of immunity among adults who were exposed as children. However, measles also killed many who were nonimmune until a vaccine was developed in 1963. Mass inoculation has allowed for its current high level of global control. Pertussis (whooping cough) is a highly contagious bacteria with overlapping syndromes to other respiratory viruses, but is controlled in the U.S., thanks to ongoing vaccination of children and antibiotic treatment (and prophylaxis) of symptomatic disease. Only increasing vaccine hesitancy among parents in the U.S. over the past 10 years has led to increasing outbreaks of pertussis.
The COVID-19 virus has features that make it unlikely to be eradicated, including its ability to live in animals, its high level of transmissibility (especially of the delta variant), its similarities to other respiratory viruses (allowing it to hide in plain sight) and the ability of the virus to be transmitted during asymptomatic or presymptomatic infection, which allows carriers to spread the disease without knowing they're making others sick.
Even though we tried masks, distancing, ventilation, testing and contact tracing to various levels of success around the world, only mass immunity can bring COVID-19 under control.
Fortunately, safe and effective vaccines for the disease were developed in a relatively short time compared to the history of any other vaccine (the first vaccine for influenza was developed in 1942, 24 years after the 1918 flu pandemic). These vaccines are the key to turning COVID-19 into an endemic — a controlled, communicable disease.
Remember that the definition of control means the reduction of disease (manifested by symptoms caused by the pathogen), not the elimination of asymptomatic cases. Since the vaccines are remarkably and persistently effective in preventing severe cases of COVID-19, they will most safely serve as our conduit to control. Antibodies generated by the vaccines will naturally wane, but the vaccines generate B cells that get relegated to our memory banks and will continue to protect us in perpetuity. T cells generated by the vaccines also protect us from severe disease and are unfazed by the variants.
So, what will COVID-19 endemicity look like? It will look like the old normal.
If we can tamp down viral circulation (an effort that requires global vaccine equity) and defang the virus (or reduce its ability to cause severe disease)
through ongoing vaccination, endemicity allows life to get back to the way it was. Outbreaks of severe disease will still occur among populations unwilling to be vaccinated, like we have seen in the Bay Area with measles, but mandates can help increase vaccination uptake.
As the ranks of the vaccinated grow and circulation of the virus decreases, COVID-19 will go the way of other respiratory viruses over which we have control, like measles. Hospitals will test those with a severe respiratory ailments and tailor treatments (antivirals, steroids and other anti-inflammatories for COVID-19) to whichever infectious agent is causing the symptoms, be it COVID-19, flu or bacterial infection. Moderate COVID-19 symptoms may be treated by your doctor with monoclonal antibodies or outpatient antivirals when available. Mild respiratory symptoms (like other common colds) will not require treatment. You'll stay home and rest up.
The burden COVID-19 continues to impose before authorities declare endemicity will be determined by localized societal priorities. Denmark dropped all safety restrictions on Sept. 10 after achieving a 74% vaccination rate (80% for those over 12) and low cases. Norway dropped restrictions on Sept. 25 at a 67% full vaccination rate. Portugal dropped most of its restrictions on Friday with an 85% vaccination rate. Ireland will lift remaining restrictions on Oct. 22 with a 90% vaccination rate (80% for those over 12)
The U.S., meanwhile, continues to suffer heavy COVID-19 hospitalizations in many states. Some regions, like California, with low hospitalizations and high vaccination rates (now over 74% first dose) are still keeping restrictions like masking in place. We here in California are on the verge of endemicity for this non-eradicable infection. A reduction in serious cases over the coming months should facilitate this transition.
COVID-19 has surprised us before, but no vaccine-preventable or immunity-inducing infection has ever raged on as an ongoing pandemic in the history of humanity. As we learned from HIV, ongoing mutations usually incur costs to viral fitness or render the virus weaker. We have a moral obligation to vaccinate the world to prevent undue suffering, but a vaccine-resistant variant (due to the in-breadth T cell response generated by the vaccines) is unlikely to emerge.
Defanging COVID-19 and stripping it of its ability to cause severe disease will relegate it to the fate of the four other circulating cold-causing coronaviruses. It will become endemic. The key to this normalcy is immunity, preferably through vaccination and not natural infection. From there, the last hurdle remains the psychological acceptance that endemicity has arrived, and that we are safe to return to normal.