COVID-19: How Omicron beat Delta in three stats

A detailed analysis in the UK showed that people infected with the Omicron variant of the coronavirus SARS-CoV-2 were nearly 50% more likely to infect people who lived with it than those infected with the Delta variant

Since the virus was first identified in South Africa in late 2021, Omega has unleashed a wave of infections and deaths in countries around the world, including places like Hong Kong, which have so far been largely unaffected by SARS-CoV-2

In the UK, Omicron was first spotted in mid-November 2021 and quickly overtook Delta as the dominant variant

Researchers from the UK Health Security Agency analysed data from 51,281 people who tested positive for Omicron or Delta and their 151,592 close contacts between 5 and 11 December 2021

The scientists found that people infected with Delta virus transmitted the virus to about 11 percent of their family members, while those infected with Omicron virus transmitted the virus to nearly 16 percent of their family members (see "Comparing Variations")

The difference was more pronounced outdoors—people infected with Delta virus transmitted the virus to about 4% of the people they came into contact with outside, while people infected with Omicron virus transmitted the virus to 8% of people, So the risk more than doubled

immune evasion

The researchers also assessed how vaccination affected people's chances of contracting both variants and found that unvaccinated family members were 23 percent more likely to contract Omicron virus than Delta virus

But in the vaccinated population, the gap widened, showing omicron's advantage in evading vaccine-induced immunity
.
Family members who received three doses of the SARS-CoV-2 vaccine were more than twice as likely to be infected with omicron as they were with Delta (see "Vaccine efficacy")
.

If a person gets three doses of the vaccine, they are about twice as likely to pass the omicron virus to another family member as the delta virus (see "Interrupting transmission")
.

Three is better than two

The data also showed that the third dose had a slight beneficial effect on the spread of both variants compared to just two doses, although the effect was greater for delta than for omicron
.
After the third injection, family members were about 32 percent less likely to be infected with Delta virus and 12 percent less likely to be infected with Omicron virus, compared with family members who had only received two injections
.
People who received booster shots were 38 percent less likely to transmit delta virus infection to family members and 22 percent less likely to transmit omicron virus infection to family members, compared with people who had only received two shots
.

Leo Poon, a virologist at the University of Hong Kong, said that although this study shows that existing SARS-CoV-2 vaccines offer limited protection against Omicron infection, other studies have shown that they are effective in preventing infections caused by the two Serious disease caused by the variant is effective
.
But he noted that the work was done while Omicron's BA.
1 subvariant was still in circulation, and now that another subvariant, BA.
2, is rapidly gaining momentum, this variant also needs to be studied
.
However, he said vaccination remains one of the most effective measures "to protect ourselves" from serious illness, hospitalisation and death
.