New research shows that two doses of either Pfizer-BioNTech vaccines or Moderna Covid-19 vaccines offer minimal protection against symptoms caused by the Omicron variant. However, a booster shot is possible to restore protection.
The study was published in the New England Journal of Medicine on Wednesday. It found that Pfizer's effectiveness against symptoms fell to 8 percent, from 65 percent after the first dose of the primary vaccine series.
The effectiveness of the Moderna vaccine's first two doses saw a similar decline, dropping to 15% from 71 percent in the same period.
The protection was restored to the levels that were seen after two doses of the Moderna or Pfizer vaccines by using a booster shot. However, the protection began to wane after approximately two months.
This study was funded by the U.K. Health Security Agency. It adds to the growing evidence that two doses (or more) of Covid vaccines offer very little protection against mild illnesses from the omicron variant. Experts however note that they still provide strong protection against serious disease and death.
According to the study authors, these findings highlight the importance of booster shots. They also wrote that third doses offer a "rapid, substantial" increase in protection against mild and severe illnesses.
According to the Centers for Disease Control and Prevention, only about half of Americans eligible for a booster have actually received one.
John Moore, an immunologist at Weill Cornell Medical College, said that the research shows that omicron is "significantly more likely to cause symptomsatic breakthrough infections than delta." He was not part of the study.
He said that it is more important to ensure your protection against death and hospitalization.
Moore stated that those who have had three doses of the medication "still have pretty substantial coverage" against symptoms.
The study covered more than 1,000,000 people who were infected with the omicron and delta variants. It was done between Nov. 27 and Jan. 12. The study only examined mild illnesses and did not consider severe outcomes like hospitalizations.
The people were vaccinated with Pfizer, Moderna and AstraZeneca vaccines.
According to the study, people who received two doses AstraZeneca vaccine (which is not currently authorized in the U.S.) also experienced a decrease in their protection against infection after several month. They also experienced a decrease in protection after receiving boosters.
Another study found that vaccines are not effective in preventing omicron infection. However, people who have received three doses of the vaccine appear to be the most protected. Studies have shown that two doses should provide high protection against serious illness, hospitalization, and death.
The CDC published a separate study on Tuesday. It found that although two doses of Pfizer vaccine didn't protect children 5 and older from an omicron infection, they kept most of them out the hospital.
Paul Offit, a pediatric vaccine expert at Children's Hospital Philadelphia, stated that people might have to accept that immunity from a previous infection or vaccination may no longer be effective in protecting against mild illnesses.
Offit, who was not part of the research, stated that this virus is one in which there is no tolerance for spreading and zero tolerance to mildly symptomatic or asymptomatic infections. "Until we accept that mildly symptomatic people will be around, even though they have been vaccinated," Offit said.