The omicron coronavirus variant has spread rapidly around the world, with fully vaccinated people increasingly reporting Covid-19 infections and governments accelerating booster campaigns to control the outbreak, but with evidence mounting that protection from booster shots also wanes, how well do vaccines protect against the virus?
Two doses of a Covid-19 vaccine or a previous infection offers little protection against symptomatic infection—almost none, in some cases—from the omicron variant compared to the delta strain, researchers say.
A CDC study published Friday found that vaccine effectiveness after a second dose was much higher before the 180 day mark than after the 180 day mark, and further showed that a booster dose was not only very effective at preventing hospitalizations, but also at preventing the need for emergency room and urgent care visits.
In a study published Friday in the Journal of the American Medical Association, researchers found that people who had three doses of an mRNA vaccine were about three times less likely to get a symptomatic omicron infection than unvaccinated people.
Preliminary data from Israel, among the first countries to roll out a fourth shot, indicate successive boosters will not be enough to protect against omicron infection and the European Medicines Agency warned frequent boosting is not a “sustainable long-term strategy.”
While protection against symptomatic infection has decline, both early data and the two new studies released Friday found vaccinated people are strongly protected against serious illness, hospitalization and death compared to unvaccinated people, which University of Arizona immunologist Professor Deepta Bhattacharya told Forbes is the “most important thing we need the vaccines to do” and “increases substantially after booster doses.”
What To Watch For
Omicron-specific shots. Many vaccine makers—including Pfizer, Moderna, Johnson & Johnson, AstraZeneca and Novavax—are developing versions of the Covid-19 vaccines specifically targeting omicron. Pfizer and Moderna have said their shots could be ready by March.
Experts believe omicron’s ability to evade immune defenses of vaccinated or previously infected people is what allowed it to rapidly overtake other variants and spread across the globe. The delta variant, in comparison, managed to spread so quickly because it caused infected people to give off larger amounts of virus. A report, which has not been peer reviewed, from researchers at Imperial College London found the risk of reinfection with omicron was 5.4 times greater than with delta, with the protection from past infection falling to just under 20% for omicron. However, experts and health agencies say vaccination is still the best available protection against omicron and the World Health Organization warned “the unvaccinated will be hit hardest.” While the high volume of breakthrough cases in vaccinated people can obscure the overall picture, data from around the world consistently shows unvaccinated people to be at far greater risk of infection, hospitalization and death than their vaccinated counterparts.
What We Don’t Know
Which vaccine is most effective against omicron. Vaccine makers testing their shots against the variant have analyzed levels of neutralizing antibodies in the blood of trial participants. These are an indicator of how well the shots may protect against infection but give an incomplete picture of immunity. Bhattacharya told Forbes Moderna shots “seem to be doing a bit better than the others” in terms of inducing neutralizing antibodies. Dr. Amesh Adalja, a senior scholar at the Johns Hopkins Center for Health Security, told Forbes: “All of the current vaccines are able to prevent what matters [serious disease] when it comes to omicron.”
“The vaccines are not magic forcefields or bug zappers,” Adalja told Forbes. “They are meant to make any infection…mild. You are getting vaccinated to prevent yourself from getting severe illness from Covid-19.”
9.7 billion. That’s at least how many doses of Covid-19 vaccine have been administered around the world, according to data collated by Johns Hopkins University. At least 11 billion doses have been delivered around the world, according to data from analytics firm Airfinity. Around half of these are inactivated-virus vaccines—mostly made by China’s Sinovac and Sinopharm, accounting for around 5 billion doses—which lab studies suggest offer practically no protection against omicron infection. A third booster dose of inactivated-virus vaccines like Sinovac and Sinopharm shots may not be able to raise the levels of neutralizing antibodies, which can help prevent the virus infecting cells, high enough to protect against omicron, though a different kind of shot like mRNA vaccine could help.
Here’s How Covid-19 Vaccine Makers Plan To Tackle Omicron (Forbes)
4th Vaccine Shot Likely ‘Not Good Enough’ To Protect Against Omicron, Israeli Researcher Says (Forbes)
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