Chennai: Some down with Covid despite getting 1st vax shot

Chennai: Amid the Covid surge, doctors noticed people testing positive despite having taken the vaccine. Senior infectious diseases experts in the city said that over the past 10 days, at least 20 patients tested positive about a week to 10 days after getting their first short.

Though the state does not have numbers, both government and private hospitals have reported such cases. “Fewer people tested positive after the second dose. Among them the infection is mild,” said Apollo Hospitals infectious diseases expert Dr V Ramasubramanian. “On the other hand, some patients who have taken one dose come in with high fever, cough, cold and other complications.”

Doctors said people testing positive after their first shot is mainly because they let down their guard, stop wearing masks and violate distancing norms. “Most vaccine centres in the city do not maintain social distancing norms or insist people wear masks while they wait inside the observation rooms for thirty minutes. It is even worse in buses, trains, religious places, malls and beaches,” said Gleneagles Global Hospitals infectious diseases expert Dr Subramanian Swaminathan. His hospital has seen about 15 such cases in the last few days, including some under treatment in the intensive care unit.
This may not have happened if vaccines were available when the rate of transmission was lower between January and February, said senior virologist Dr Jacob John. “This is the reflection of the speed of transmission of the virus. The infection rate for UK strain is two times higher than the mother virus,” he said.

While the vaccine is effective after two doses, it is “guesstimated” that the chance of getting Covid-19 is around 10% less in a person who has taken the first dose of the vaccine compared to those who have not taken the vaccine. Studies have shown that the effect of Covaxin is more than 80% two week after the second dose if it is taken 28 days after the first dose.“In theory, recipients can boost the efficacy to 90% or more with the third dose,” he said.

For Covishield, the effectiveness goes up to 80% if the second dose is delayed by up to 12 weeks. “The efficacy graph goes up from about 52% when given after 28 days to up to 82% when administered in the 12th week,” John said.