Igh A study published in JAMA Network is open Today, scientists are reporting how effective the original vaccine and the booster shots are against the COVID-19 Delta and Omicron variants.
Researchers in Ontario analyzed data from more than 134,000 people, including those who tested positive for Delta and Omicron infection through December 2021. They found that people who were fully vaccinated (with two doses of the mRNA vaccine, either from Moderna or Pfizer-BioNTech) experienced a decrease in Vaccine efficacy against delta and omicron infections, but the decrease was greater against omicron than against delta. Among the vaccinated, the effectiveness of the injection decreased from 36% to two months after the second dose of the initial series, to 1% after four months (or six months after the second dose).
The booster doses helped restore some of the vaccine’s effectiveness, putting it up to 61% against Omicron beginning a week after people received the booster vaccine.
“The key message is that against Omicron, you really need three doses for optimal protection against severe outcomes,” says Dr. Jeff Kwong, chief scientist at ICES (a not-for-profit research institute) and senior author of the study. “The two doses were good enough against Delta, but since last December, when Omicron took over, two doses don’t provide enough protection.”
The study did not explore how long this protection lasts after the third shot, or the first booster dose. US health officials are now recommending that people receive another booster dose, the first one Specifically targeting the omicron. The booster contains the genetic sequences of Omicron BA.4/5, which now causes nearly all new infections of COVID-19. Based on data from his study, which showed diminished protection after the initial vaccination series, Kwong expects that the same will happen after the first boost. If the antibodies are diminished, people are less protected from contracting the virus.
On the positive side, the Kwong study confirmed previous data showing that vaccinated people who also received a first booster dose remain protected from becoming seriously ill from COVID-19, even if they have Omicron; Vaccine efficacy against severe disease was about 95% a week or more after the third dose. the new Omicron-based booster, which targets both the original variants and the Omicron BA.4 / 5 variants, is “definitely a good step,” says Kwong, to better protect people from infection. But he says, “My concern is that there could be another variant showing up with other mutations. And this Omicron booster may or may not help against that.”
Kwong says the study data is a good reminder that vaccines cannot provide optimal protection, especially against infection. Therefore, other measures may be more effective, including wearing masks and avoiding crowded, poorly ventilated indoor gatherings. “We need other measures to better protect ourselves, and concealment is the measure that doesn’t care about the variable that is being traded,” he says. “It’s unfortunate that masks have become so politicized, but the more people who wear masks, the more protected everyone becomes.”
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