Emphasising that the Omicron variant is infecting both vaccinated and unvaccinated people worldwide, WHO Chief Scientist Dr. Soumya Swaminathan has said that it appears that Covid-19 vaccines are still proving to be effective because even though the numbers are going up exponentially in many countries, the severity of the disease has not surged to a new level.
"As expected, T cell immunity holding up better against #Omicron. This will protect us against severe disease. Please get vaccinated if you have not," said Swaminathan in a tweet on Wednesday.
Either vaccines or prior infections with Covid-19 trigger human T cell response. Explaining factors that account for vaccine's effectiveness against Covid-19, Swaminathan virtually at the WHO press briefing on Wednesday said that vaccine effectiveness varies a little bit between vaccines though the majority of all of the WHO Emergency Use Listing vaccines actually have very high rates of protection against severe disease and death at least till the delta variant.
She also said that there are biological factors also that decide a vaccine's effectiveness. "It includes age, underlying illnesses and we know and proved it with all the variants that the older you are the more the underlying illnesses and co-morbidities the more vulnerable you are to get the disease," she said.
Referring to the third factor which decides the effectiveness of the Covid-19 vaccine against Omicron variant, Swaminathan said, "It is the time since vaccination and the waning of the immunity and we know that there is some amount of meaning but again there is more waning for infection against infectious and that is why we are seeing a lot of breakthrough infections now especially with Omicron because Omicron does have the capacity to overcome pre-existing immunity, and needs higher levels anti-bodies and protection."
Further, she said that now the evidence on Omicron is just emerging and it would still be premature to conclude definitely but all of the lab studies are pointing towards a reduction in neutralisation capacity and also what it is clinically seen that people who have been vaccinated, people who have had prior infections are still getting breakthrough infections with Omicron.