The family of a child who died of meningitis B have said they are "disgusted" with the government's refusal to vaccinate older children.
Two-year-old Faye Burdett died in 2016 – she was too old to have the vaccine.
An 820,000-signature petition calling for all children to be vaccinated was then submitted, – but the idea was rejected as "not cost effective".
And campaigners are still waiting for a promised government report into how that decision was reached.
Health Minister Steven Brine will face questions from MPs on Tuesday over why that report – looking at the cost-effectiveness of vaccines, including the Men B jab – still hasn't been published.
In 2016, experts from the Joint Committee on Vaccination and Immunisation (JCVI) advised the government it would not be cost-effective to offer the Men B jab to children between two and 11, because of the low levels of meningitis B in older children.
Faye's parents, Jenny and Neil Burdett, said they "remain disappointed and frustrated that the government deemed the protection of vulnerable children as 'not cost effective'.
"We had hoped our collective voices would be heard and changes made," they said.
"We are disgusted with the health department for the way they have treated one of the biggest petitions to date."
They made public photos of Faye in hospital to raise awareness of the bacterial infection.
And the petition the images featured in became the most popular petition in parliamentary history. It is now the third largest.
The charity Meningitis Now said it hoped Mr Brine would be "fully prepared to provide answers" to the people who had signed the petition and had "been patiently waiting to see its contents".
- Meningitis B is a bacterial infection that most often affects children younger than one
- Since 2015, children under 12 months have been offered the vaccination
- There are about 1,200 meningitis B cases each year in the UK
- Symptoms include a high fever with cold hands and feet, confusion, vomiting and headaches
- But a recent study warns fever might not be present and to look out for poor feeding, lethargy and irritability too
- With early diagnosis and antibiotic treatment, most people will make a full recovery
- It is fatal in one in 10 cases
- About one in four of those who survive is left with long-term problems, such as amputation, deafness, epilepsy and learning difficulties
Chief executive Dr Tom Nutt said: "We are disappointed that this important and potentially life-saving report on the future of vaccines remains unpublished and without a firm commitment from the government to consult on its findings and recommendations.
"When the petition was rejected in 2016, the then health minister cited this report as being integral to the future of vaccines and in doing so 'put on hold' the hopes of those who had signed the petition – people who had been deeply moved by the sad and preventable death of two-year-old Faye Burdett."