Omicron cases doubling in 1.5 to 3 days in areas with community transmission: WHO

“There is consistent evidence that Omicron has a substantial growth advantage over Delta. It is spreading significantly faster than the Delta variant in countries with documented community transmission, with a doubling time between 1.5–3 days,” the WHO said.

The number of Omicron cases is doubling in 1.5 to three days in areas with community transmission and infections pertaining to the new variant have been reported from 89 countries, the World Health Organization (WHO) said on Saturday.

“There was, however, higher effectiveness two weeks after a Pfizer BioNTech-Comirnaty booster, which was slightly lower or comparable to that against Delta,” the WHO said. (Reuters)

“There is consistent evidence that Omicron has a substantial growth advantage over Delta. It is spreading significantly faster than the Delta variant in countries with documented community transmission, with a doubling time between 1.5–3 days,” the WHO said in a media advisory.

The UN health body also said it was uncertain about how much can the rapid transmission of Omicron could be because of escaping immunity against the disease.

“Omicron is spreading rapidly in countries with high levels of population immunity and it remains uncertain to what extent the observed rapid growth rate can be attributed to immune evasion, intrinsic increased transmissibility or a combination of both,” it said.

“However, given current available data, it is likely that Omicron will outpace Delta where community transmission occurs,” it added.

The WHO said there was only limited data regarding the clinical severity of the disease caused by the variant and more data was needed to understand the severity and how it was impacted by vaccination and existing immunity.

However, the global health body also warned increasing cases could choke healthcare systems.

“Hospitalizations in the UK and South Africa continue to rise, and given rapidly increasing case counts, it is possible that many healthcare systems may become quickly overwhelmed,” it said.

Preliminary findings from England indicated a “significant reduction” in vaccine effectiveness against the symptomatic disease of Omicron as compared to the Delta variant following two vaccine doses of either the Pfizer BioNTech or the AstraZeneca vaccines, the WHO said.

“There was, however, higher effectiveness two weeks after a Pfizer BioNTech-Comirnaty booster, which was slightly lower or comparable to that against Delta,” it also said.

It warned that the preliminary findings need to be considered with caution as the “designs may be subject to selection bias and the results are based on relatively small numbers.”