A number of Hertfordshire schools have brought in measures to curb the spread of Covid-19 – with more than 100 outbreaks reported in educational settings across the county.

Last year staggered starts, keeping children in ‘bubbles’, social-distancing and the wearing of face masks – as well as periods of closure and home-schooling – were the norm for schools across the county.

But in line with national changes, when schools reopened in September the measures were no longer routinely required.

Now it has emerged there are currently 112 Covid-19 outbreaks in educational settings across the county.

Related: Rise in coronavirus cases in Chorleywood linked to school

On the advice of public health officials, some schools in Hertfordshire have already brought back a number of measures designed to halt the spread of the virus.

Some schools are understood to have reintroduced face coverings, others have changed circulation routes around the school and some have told children to remain at home.

Ventilation measures and CO2 monitors have been made available. And in some cases schools have been told to cancel events such as open days or sports days.

Hertfordshire’s director of public health Jim McManus says it is currently a "mixed picture" across the county’s 600 schools .

While cases in some schools have not risen very quickly, he says there are some schools where numbers have risen so quickly that it has "surprised" them.

And overall he says school numbers are "higher than I would like them to be".

Some parents, Mr McManus accepts, have suggested they should not be taking the additional measures.

But for every one of that opinion, he says he is contacted by 10 who back the approach and say they want it to be taken as seriously as possible.

And he says that if they need to do more, they will.

According to the county council there are currently 112 confirmed outbreaks in educational settings – including schools, nurseries, colleges childminders – in Hertfordshire.

An outbreak is recorded when five children pupils, students or staff (or 10 per cent of that group) – who are likely to have mixed closely – test positive for Covid-19 within a 10-day period.

The most recent figures show that the rate of infection amongst 12-15 year olds in Hertfordshire is 1,674 per 100,000 population. That compares to an overall case rate in Hertfordshire of around 350.

Mr McManus revealed in a media briefing on Tuesday that of the 63,624 12 to 15-year-olds in the county, 10.5 per cent had received a dose of the Covid vaccine within the last week.

The public health director said vaccine uptake in this age group had been "higher than expected".