Ideas
February 10, 2022 10:19 AM EST
Hanage is Co-Director of the Center for Communicable Disease Dynamics and an associate professor of epidemiology at the Harvard T.H. Chan School of Public Health, where he studies the evolution and epidemiology of infectious disease

Over the past couple of weeks, I’ve started to notice twinges of a feeling to which I have become unaccustomed. At first I thought it was indigestion, but I’m beginning to think it is actually cautious optimism. That’s because the recent Omicron surge underscored how well our COVID-19 vaccines are working.

Omicron was first documented in Botswana and South Africa in late November, 2021, and rapidly spread around the world. Yet something was different this time around. Compared with the Delta variant, Omicron infection resulted in notably lower hospitalization and death rates in South Africa and elsewhere.

There has been a rush to declare Omicron “milder” than Delta, and before we spend any time thinking about whether it is, we should remember that this “mild” virus was responsible for more than 15,000 deaths in the U.S. over the last week alone. And a virus this transmissible does collateral damage by infecting healthcare workers who must then isolate.

Having said that, at the peak of Omicron, the U.S. reported about ten times more daily infections than were recorded in the middle of November when Delta was the only variant in town. The Omicron peak however resulted in about twice as many deaths as we saw in the middle of November. It should be clear that were we seeing this many infections with Delta, things would be much, much worse than they are.

Three explanations are plausible: First, Omicron causes an inherently less severe disease, the vaccinations are working, or some combination of the two. It is hard to disentangle them because the Omicron wave in South Africa came hard on the heels of the Delta one, and at a point when vaccination had been delivered to a substantial fraction of the population. As a result, the variant emerged into a population with the benefit of more immunity than at any previous stage of the pandemic.

Given that Omicron is somewhat able to evade previous immunity, there have been significant numbers of reinfections in people with previous SARS-CoV-2 infections as well as breakthrough cases in vaccinated and boosted people. Closely examining the data from South Africa, a colleague and I determined that at least some of the apparently mild nature of Omicron is indeed due to immunity keeping people out of the hospital. That is consistent with another study, which shows the risk of a vaccinated person being admitted to the hospital for Omicron infection is reduced by 70%, compared with an unvaccinated person.

Second, side by side comparisons of people infected with each variant in the last few months suggest that Omicron is somewhat less inherently dangerous than Delta. Whether this holds up in older age groups remains to be seen, but again the data are more comforting than might have been feared.

Third, people who are vaccinated are also less likely to spread SARS-CoV-2, including the recently isolated BA.2 subvariant of Omicron, which appears even more infectious than the original BA.1 Omicron subvariant identified last November. BA.2 is also more able to escape vaccine coverage than BA.1, yet those who are vaccinated were less likely to infect the people living in the same household, according to a recent study in Denmark.

Underscoring the importance of vaccination is a comparison of cumulative death rates for the pandemic and the Omicron surge in the U.S. and other high-income countries. Wealthy countries with high vaccination rates are faring substantially better than the U.S., where our vaccination and booster rates are disturbingly low. This stark juxtaposition shows how powerful vaccination can be for keeping our neighbors and loved ones safe. Remember that a vaccination rate of 80% is not “almost as good” as 90%; on the contrary, it is twice as bad because it leaves 20% rather than 10% without the benefit of vaccination. And in a country as large as the U.S. that 10% adds up to about 20 million adults.

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The success of the vaccines is wonderful news indeed. And yet obtaining a vaccination can still be a difficult feat. Colleagues at Ariadne Labs created a tool that shows on a map how far someone needs to travel to obtain a vaccination. According to their analysis, the U.S. is pockmarked with areas where people who want to be vaccinated must drive 30 minutes or more to a vaccination site. If someone relies on public transportation or is trying to vaccinate a child or teenager, large swaths of the country require at least a 30-minute trip to access vaccinations. For those dealing with multiple jobs, limited physical mobility, childcare, elder care, or other responsibilities, such a journey can too difficult to make. Vaccination must be easily and readily available to all.

And as we all know, SARS-CoV-2 is an adept and agile adversary. As I write this, the virus is currently infecting more than 2.8 million people worldwide, and each one of those infections is an opportunity for the virus to mutate into a more—or less— infectious or lethal variant. This vast number of active infections practically guarantees that we will see more SARS-CoV-2 variants. Our best hope is that by immunizing everyone possible, the consequences will not become even more grave. We may not get so lucky with the next variant.

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