According to a study, the chance of reinfection with the Omicron variant of the coronavirus is more than five times higher compared to that of Delta, and it shows no signs of being milder, as cases spread across Europe and endanger year-end celebrations.
Imperial College London's findings were based on data from the UK Health Security Agency and the National Health Service on patients who tested positive for Covid-19 in a PCR test in England between November 29 and December 11.
"We find no evidence (for both risk of hospitalisation attendance and symptom status) of Omicron having different severity from Delta," the study said, although it added that data on hospitalisations remains very limited.
"Controlling for vaccine status, age, sex, ethnicity, asymptomatic status, region and specimen date, Omicron was associated with a 5.4-fold higher risk of reinfection compared with Delta," the study, which was dated Dec. 16, added.
Previous infections from the virus may provide as little as 19 per cent protection against reinfection by the Omicron variant, Imperial College (ICL) said in a statement> It however stressed that the research had yet to be peer reviewed.
The researchers discovered that those who were had taken a double dosage of a Covid-19 vaccine and had got their booster dose two or more weeks ago had a considerably higher probability of having asymptomatic Omicron illness compared to those who were two or more weeks past their first vaccine dose.
Vaccines from AstraZeneca and Pfizer were used in the trial.
This leads to vaccination effectiveness of between 0 per cent and 20 per cent following a double dosage of a vaccine, and between 55 per cent and 80 per cent with a booster dose. This conclusion however depends on the estimates used for vaccine effectiveness against symptomatic infection from the Delta variant.
"This study provides further evidence of the very substantial extent to which Omicron can evade prior immunity given by both infection or vaccination," study lead Professor Neil Ferguson said in ICL's statement.
"This level of immune evasion means that Omicron poses a major, imminent threat to public health."
However it was important to not overinterpret the data, said Dr Clive Dix, former Chair of the UK Vaccine Taskforce.
"The conclusions made are based on making assumptions about Omicron where we still don't have sufficient data," Dr Dix said. "For example, we have no data on the cellular immune response which is now probably driving effectiveness of vaccines."
"This is a crucial missing assumption in the modelling."
The conclusions derived from the UK study were apparently in contrast to similar parameters in data coming out of South Africa, where the Omicron variant was first identified. Data from South Africa shows that Covid-19 vaccines are reacting strongly against the latest variant in preventing severe cases and even deaths, he said.
"There is a huge amount of uncertainty in these modelled estimates and we can only be confident about the impact of boosters against Omicron when we have another month of real-world data on hospitalisation ICU numbers and deaths," he said.
(Source:www.reuters.com)
Imperial College London's findings were based on data from the UK Health Security Agency and the National Health Service on patients who tested positive for Covid-19 in a PCR test in England between November 29 and December 11.
"We find no evidence (for both risk of hospitalisation attendance and symptom status) of Omicron having different severity from Delta," the study said, although it added that data on hospitalisations remains very limited.
"Controlling for vaccine status, age, sex, ethnicity, asymptomatic status, region and specimen date, Omicron was associated with a 5.4-fold higher risk of reinfection compared with Delta," the study, which was dated Dec. 16, added.
Previous infections from the virus may provide as little as 19 per cent protection against reinfection by the Omicron variant, Imperial College (ICL) said in a statement> It however stressed that the research had yet to be peer reviewed.
The researchers discovered that those who were had taken a double dosage of a Covid-19 vaccine and had got their booster dose two or more weeks ago had a considerably higher probability of having asymptomatic Omicron illness compared to those who were two or more weeks past their first vaccine dose.
Vaccines from AstraZeneca and Pfizer were used in the trial.
This leads to vaccination effectiveness of between 0 per cent and 20 per cent following a double dosage of a vaccine, and between 55 per cent and 80 per cent with a booster dose. This conclusion however depends on the estimates used for vaccine effectiveness against symptomatic infection from the Delta variant.
"This study provides further evidence of the very substantial extent to which Omicron can evade prior immunity given by both infection or vaccination," study lead Professor Neil Ferguson said in ICL's statement.
"This level of immune evasion means that Omicron poses a major, imminent threat to public health."
However it was important to not overinterpret the data, said Dr Clive Dix, former Chair of the UK Vaccine Taskforce.
"The conclusions made are based on making assumptions about Omicron where we still don't have sufficient data," Dr Dix said. "For example, we have no data on the cellular immune response which is now probably driving effectiveness of vaccines."
"This is a crucial missing assumption in the modelling."
The conclusions derived from the UK study were apparently in contrast to similar parameters in data coming out of South Africa, where the Omicron variant was first identified. Data from South Africa shows that Covid-19 vaccines are reacting strongly against the latest variant in preventing severe cases and even deaths, he said.
"There is a huge amount of uncertainty in these modelled estimates and we can only be confident about the impact of boosters against Omicron when we have another month of real-world data on hospitalisation ICU numbers and deaths," he said.
(Source:www.reuters.com)
