London, Nov 19 (IANS): The UK health body has delayed the second Covid jab for children aged between 16 and 17 with infection to 12 weeks, from the earlier four weeks.

The UK Health Security Agency issued the "precautionary advisory" to prevent the small risk of heart inflammation among young kids.

"For those aged 16 to 17 who have had coronavirus (Covid-19) infection, the second vaccine dose should be given 12 weeks or more following the first vaccine dose, or 12 weeks following a positive Covid-19 test result - whichever is later," the agency said in a statement.

"This increase from 4 weeks is based on the emerging evidence from the UK and other countries, which suggests that leaving a longer interval between infection and vaccination may further reduce the already small risk of myocarditis in younger age groups," it added.

The risk of the heart problem was extremely low -- latest data suggests nine cases of myocarditis can be expected to be seen among children for every one million doses given, UKHSA said. Cases to date have been mild and recovered quickly with treatment.

"The Covid-19 vaccines are very safe. Based on a highly precautionary approach, we are advising a longer interval between Covid infection and vaccination for those aged under 18," said Dr Mary Ramsay, Head of Immunisations at UKHSA, in the statement

Vaccines have been available to 12 to 15-year-olds in the UK since September. So far, over half of 16 and 17-year-olds have come forward for the first dose and nearly a third of 12 to 15-year-olds.

Further, the UKHSA said the advice should not affect spread of the virus given the protection offered by natural infection. It said natural infection provided good protection against re-infection for three to six months.

Around 30 per cent of children are thought to have been infected by Covid in recent months, according to official estimates based on antibody tests.

"Young people and parents should be reassured that myocarditis is extremely rare, at whatever point they take up the vaccine, and this change has been made based on the utmost precaution," Ramsay added.

However, those aged 18 and above should still take up their vaccine offer if they are 4 weeks post a positive test. This is because they are at higher risk of the complications of Covid-19 infection, the agency said.

The advice is also not for those aged 12 to 17 in clinical at-risk groups. These individuals should still take up their vaccine offer if they are 4 weeks post a positive test and continue to receive their second dose 8 weeks after the first. This is because their individual risk of severe outcomes from Covid-19 is higher and so outweighs any benefit of delaying to 12 weeks, the advisory said.