The protection that a Pfizer booster shot gives against the new coronavirus variant Omicron, following a “Pfizer primary course,” drops to just 45% after 10-plus weeks, according to a new study.
A booster shot from Moderna fared better, the study from the United Kingdom Security Agency (UKSA) said.
“In all periods, effectiveness was lower for Omicron compared to Delta,” the report said. “Among those who received an AstraZeneca primary course, vaccine effectiveness was around 60% 2 to 4 weeks after either a Pfizer or Moderna booster, then dropped to 35% with a Pfizer booster and 45% with a Moderna booster by 10 weeks after the booster. Among those who received a Pfizer primary course, vaccine effectiveness was around 70% after a Pfizer booster, dropping to 45% after 10-plus weeks and stayed around 70 to 75% after a Moderna booster up to 9 weeks after booster.”
“These results should be interpreted with caution due to the low counts and the possible biases related to the populations with highest exposure to Omicron (including travelers and their close contacts) which cannot fully be accounted for,” the report said.
Still, the report suggests that getting a booster shot is effective at preventing severe illness and hospitalization. “There are insufficient severe cases of Omicron as yet to analyze vaccine effectiveness against hospitalization, but this is expected to be better sustained, for both primary and booster doses,” the report said.
Adam Finn, a member of the group of experts who advise the British government, said more research is needed on Omicron to determine if a fourth dose will be recommended.
“We do need to see how things go through this wave and beyond. I think there may well be people who received their boosters early who are in the older, more vulnerable age groups who may need a further jab — that has not been decided yet,” Finn told LBC Radio, Insider reported.
On Monday, Moderna announced that its tests have shown that its booster shot of the coronavirus vaccine significantly raises the level of antibodies to battle the Omicron variant.
The pharmaceutical company’s testing shows that “the currently authorized booster dose of 50 micrograms — half the dose given for primary immunization — increased the level of antibodies by roughly 37-fold, the company said,” according to The New York Times. “A full dose of 100 micrograms was even more powerful, raising antibody levels about 83-fold compared with pre-boost levels, Moderna said.”
The company did say, however, that its booster shot “produced side effects comparable to those seen after the two-dose primary series. But the dose of 100 micrograms showed slightly more frequent adverse reactions relative to the authorized 50-microgram dose,” said the Times.
Meanwhile, a new study of early data about the Omicron variant has found that the most common symptoms are akin to the common cold.
The ZOE COVID Symptoms Study, which has been tracking symptoms reported by participants using a smartphone app, reported that the top five symptoms for Omicron are runny nose, headache, fatigue (mild or severe), sneezing, and sore throat. The data were collected between December 3 and 10 in London.