With recent news about the Covid-19 pandemic, I figured it was time again for a covid update post. Feel free to review my previous post in this series as I reference some of its information.
Omicron Variant
The Omicron variant, otherwise known as B.1.1.529, was first detected in South Africa in November 2021. Within days, it was declared a variant of concern by the WHO and is now the dominant strain in many countries, accounting for over 70% of new cases in the United States. Scientists are still trying to determine the R0 value of the Omicron variant, but some have predicted that it could be as high as 10. If true, this would make Omicron over three times as infectious as the original Covid-19 (2.79) and about 50% more infectious than the Delta stain (7), though still slightly lower than that of diseases like chicken pox and measles (12-18). Now, there is data to suggest that Omicron might cause less severe disease than the Delta strain, with proportionally fewer Omicron patients requiring intensive care. That said, this strain could still be more deadly than previous ones due to its higher transmission rate. There is still the potential that more people will fall severely ill and die with Omicron than with previous strains simply due to how fast this strain spreads and how much pressure it’s thus putting on our healthcare system.
Perhaps the biggest question among researchers is how effective are existing Covid vaccines against the Omicron strain. Omicron viruses have over 50 mutations separating it from the original Covid-19, 30 of these being on the spike protein. Since it’s this protein that vaccines target, there are concerns that this protein might be different enough to no longer be an effective target for existing vaccines. While research is still ongoing, current data puts the Pfizer and Moderna vaccines somewhere around 40% effective at preventing Omicron infection and 70% effective at preventing severe Omicron symptoms. Evidence does show that the antibody response against Omicron in patients who’ve received a booster shot is significantly higher than patients who have not, so receiving a booster appears to be necessary to be properly protected from Omicron.
This brings us to breakthrough cases, when fully vaccinated patients get sick. The rates of breakthrough infections of Omicron do appear to be significantly higher than previous strains, with Covid cases among vaccinated people sharply rising in recent weeks. But this is not to say that the vaccine is ineffective against Omicron, far from it. Covid cases amongst fully vaccinated patients are much milder, with vaccinated patients being only 30% as likely to be hospitalized as non-vaccinated patients. Breakthrough infections are not a sign that a vaccine is failing; seasonal flu vaccines tend to be between 40% and 60% effective and the vaccines currently used against mumps and chickenpox (some of the most effective currently in use) are only 88% and 85% effective respectively. A vaccine doesn’t need to be 100% effective at preventing all illness to provide incredible protection to individuals or radically reduce a disease’s risk to the public.
Getting vaccinated (and boosted) is still the best way to combat Covid, both on an individual and societal level. This is not to say that one should abandon caution once they’re vaccinated; one should continue to wear masks in public and get tested before attending social events. Even though the pandemic may get worse before it gets better, there are still things we can do to protect ourselves and each other.
Endemic
The vast majority of epidemiologists believe that the Covid-19 pandemic will end with the virus becoming an endemic disease. I’ve briefly touched on this concept before, but to reiterate, the R0 of a disease is only the average number of people one person will infect IF you assume the entire population is vulnerable to getting infected. As more and more people develop an immune response to the disease, either by vaccination or by natural infection, each patient will infect fewer people and the disease’s effective reproduction number (Re) starts to go down. Once the Re drops to 1 (each infected person infects only one other person), the disease becomes endemic. At this point, Covid-19 essentially becomes akin to the flu in regards to infection rate. Instead of a world-stopping global disease, Covid will cause discreet, local outbreaks that, while bad, can be managed by national and local health services. This is what happened to the 1918 Spanish flu pandemic and to other major flu outbreaks. We might even have regular booster shots to keep the Re low much like our yearly flu vaccine.
So how close are we to Covid-19 becoming endemic? Not close. The Re of a pathogen can vary depending on region, but in the United States, most data suggests an Re between 1 and 2. Before the outbreak of the Omicron strain, there were predictions that Covid-19 could become endemic before the end of 2022. This prediction has been discredited by the new strain, but it’s hard to tell in what direction. It has been suggested that the surge in infections created by Omicron could bring us closer to the number of immune people needed for herd immunity, but it has also been suggested that the number of breakthrough cases might mean that an Re of one becomes even harder to reach.
There are currently too many questions to answer before we can know when the pandemic will end. What new strains are going to crop up next and how will they affect the math? How much protection does a previous infection with one strain give you against other strains? (It should be noted that there have been more cases of breakthrough infections for people who were previously infected with earlier Covid variants than for those who were vaccinated. Evidence indicates that even if you have had Covid before, you should still get vaccinated.) And finally, is the virus becoming endemic enough? There are concerns that given how widespread Covid-19 is, an Re of 1 could still result in enough sick people to overtax hospitals and threaten immunocompromised or impoverished people. Reaching endemic status is the bare minimum needed to end the pandemic, we’re not sure what else is needed.
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