The number of confirmed meningitis cases linked to the outbreak in Kent has been revised downward from 23 to 20, according to health officials.

The UK Health Security Agency (UKHSA) announced on Sunday that three cases originally classified as confirmed have been re-evaluated following further testing and are no longer considered confirmed.

In its latest update, the UKHSA reported that the number of suspected cases currently under investigation has also decreased, dropping from 11 to nine. This brings the overall number of cases down to 29, a reduction from the 34 cases reported the previous day.

The agency noted that additional cases might be reclassified in the coming days as more laboratory tests are conducted.

Of the 20 confirmed cases, 19 are identified as meningitis B, also known as MenB, and each case required hospitalization.

As the campaign to vaccinate thousands of young people in Kent continued into a fourth day, dozens of those eligible again queued up around the county for the vaccine or preventive antibiotics.

The length of the lines has dropped considerably since the rollout began on Wednesday, with no queue at all outside the previously busy vaccination site on the University of Kent’s Canterbury campus at 10am on Sunday.

NHS Kent and Medway said more than 8,000 MenB vaccines and 12,157 antibiotics had been handed out by 6pm on Saturday. There are six clinics providing antibiotics and vaccines across the county, while eligible University of Kent students who have returned home elsewhere can access both from their local GPs.

Two students have died in the outbreak. They are 18-year-old Juliette Kenny, a sixth-former who was described by her family as “fit, healthy and strong”, and a University of Kent student who has not been publicly named.

Dr Sherine Thomas, an infectious diseases consultant at UKHSA, said: “We continue to remain vigilant for new cases and work closely with NHS England and local authorities across the country to ensure that any new cases identified are responded to as quickly as possible.

“It’s reassuring to have seen so many eligible young people come forward for antibiotics and vaccination, and we’d like to thank everyone involved in this effort so far.

“Although the risk to the wider population remains low, it is still really important that people know the symptoms of invasive meningococcal disease and seek immediate medical attention if they or anyone they know develops them. UKHSA continues to work with partners to identify contacts and offer necessary treatment.”

An NHS Kent and Medway spokesperson said: “Our teams have been working overtime this weekend and into the evenings during the week to deliver antibiotic and vaccine clinics as fast as possible.”

Staff at the University of Kent’s Canterbury campus clinic said on Saturday that the vaccine rollout had become a “slick operation”, as queues and waiting times were now significantly shorter than during the week.

Kent County Council’s director of public health, Dr Anjan Ghosh, warned on Friday that “small household, sporadic clusters” could appear in other parts of the UK as students who have travelled away from Kent “incubate” the illness. But he said these would be “containable” and stressed that the risk of infection between individuals remained low.