Bob Johnson (Meningitis Trust) and Prof David Goldblatt (UCL)
Teenagers may need a booster dose of meningitis C vaccine, say researchers who found immunity can fall over time.
In a study of 1,000 children, more than 20% of adolescents aged 11 to 13 - a group at high risk of infection - appeared to have inadequate protection.
The long-term protection offered by the vaccine seemed to depend on the age a child was immunised, the study, in the British Medical Journal, found.
But the Department of Health said cases had not risen among adolescents.
A meningitis C catch-up campaign offered a single injection for all children aged between one and 18 in 1999/2000.
Researchers assessed the immunity of almost 1,000 six- to 15-year-olds, five years after they were vaccinated at school as part of the government campaign.
Those who were 10 years or older at the time of vaccination seemed to have ongoing protection.
But antibody levels in those aged six to eight years when they were immunised showed more than 20% had insufficient protection, researchers said.
These children are now entering adolescence.
Since 2006, infants have received two doses of meningitis C at three and four months of age, and a booster at 12 months.
It is as yet unclear whether they will also need further doses of the vaccine as they get older.
Study leader, Dr Matthew Snape, a senior clinical researcher in the Oxford Vaccine Group, said a booster jab for teenagers may be appropriate.
"Over the next few years children who were immunised between the ages of one and six will be entering adolescence and it's important to maintain immunity to meningitis C in this age group."
He added there were already vaccines given at around age 13 so the meningitis C vaccine could, in theory, be added to existing programmes.
Professor Adam Finn, head of the Bristol Children's Vaccine Centre, said adolescent boosters would probably be introduced at some point but there was no real urgency.
"There is not likely to be a resurgence of meningitis C, even if adolescents are not well protected, because there is little disease circulating.
"This research shows at some point a booster will probably be necessary but because of herd immunity, it does not need to be immediate."
A spokesperson for the Department of Health said: "There has been no rise in meningitis C cases in teenagers. Research suggests it would be many years before this could happen.
"We agree that good quality disease surveillance is important. If a problem was identified, we would step in with a booster as appropriate."
In April, a government report revealed that there were no deaths from meningitis C among under-19s in England last year.
Before routine immunisation was introduced in 1999, up to 78 children a year were killed by the infection.