We should not expect COVID-19 to become an endemic virus - scientist

Although endemic disease can occur in very large numbers, the number of cases does not change rapidly as seen with the coronavirus, she said.

“If case numbers do change [with an endemic disease], it is slowly, typically over years,” she said via email. “Epidemic diseases, on the other hand, rise rapidly over periods of days to weeks.”

Scientists use a mathematical equation, the so-called R naught (or R0), to assess how quickly a disease is spreading. The R0 indicates how many people will catch a disease from an infected person, with experts at Imperial College London estimating Omicron’s could be higher than 3.  

If a disease’s R0 is greater than 1, growth is exponential, meaning the virus is becoming more prevalent and the conditions for an epidemic are present, MacIntyre said.

“The public health goal is to keep the effective R — which is R0 modified by interventions such as vaccines, masks or other mitigations — below 1,” she told CNBC. “But if the R0 is higher than 1, we typically see recurrent epidemic waves for respiratory transmitted epidemic infections.”

MacIntyre noted that this is the pattern that was seen with smallpox for centuries and is still seen with measles and influenza. It’s also the pattern unfolding with Covid, she added, for which we have seen four major waves in the past two years. 

Covid will not magically turn into a malaria-like endemic infection where levels stay constant for long periods. It will keep causing epidemic waves, driven by waning vaccine immunity, new variants that escape vaccine protection, unvaccinated pockets, births and migration.

“This is why we need an ongoing ‘vaccine-plus’ and ventilation strategy, to keep R below 1 so we can live with the virus without major disruptions to society,” MacIntyre said, adding a warning that “there will be more variants coming.”

Last week, the World Health Organization warned that the next Covid variant will be even more contagious than Omicron.

Maria Van Kerkhove, WHO’s Covid-19 technical lead, warned against buying into theories that the virus will continue to mutate into milder strains that make people less sick than earlier variants.

The next variant of concern will be more fit, and what we mean by that is it will be more transmissible because it will have to overtake what is currently circulating. The big question is whether or not future variants will be more or less severe,

she said.

Global Biosecurity, the Twitter account representing a collective of UNSW research departments covering epidemics, pandemics and epidemiology, argued last year that Covid will continue to “display the waxing and waning pattern of epidemic diseases.”

″[Covid] will never be endemic,” the organization said. “It is an epidemic disease and always will be. This means it will find unvaccinated or under-vaccinated people and spread rapidly in those groups.”