Hospital admission

This is the part most people picture when they imagine gene therapy: the hospital stay. It is the longest continuous stretch of the whole process, and the one families plan their lives around.

How long you are in for

NHS England says the stay is four to six weeks, while the treated cells settle into the bone marrow and start making blood.

It is worth knowing that figure comes from its announcement about thalassaemia, and that in the clinical trials the stay was often longer. The middle figure was 47 days, and the range ran from about a month to nearly four months. Plan for six weeks; do not be alarmed if it runs past that.

The Casgevy patient leaflet puts it more plainly than any timescale: "The length of time for sufficient recovery can vary."

Protective isolation

After conditioning chemotherapy, your immune system is almost entirely gone until the new cells take hold. Protective isolation is how the hospital keeps infection away from you during that window.

The following describes stem cell transplant units generally rather than gene therapy specifically, but the arrangements are the same because the procedure is the same.

• A single room with its own sink, shower and toilet, and an emergency call button.

• A filter system keeping the air clean, with doors and windows kept closed.

• The room cleaned and bedding changed every day, and your own belongings wiped down regularly.

• Everyone entering, staff and visitors, cleaning their hands first.

• Usually two or three named visitors allowed into the room. Others may be able to visit once your blood counts recover, or talk to you by phone from outside.

• A 'safe' diet for the first few weeks that avoids foods more likely to carry infection, such as unpasteurised cheese.

Rules on children visiting differ between hospitals, because school and nursery bring more infections with them. That is a question worth asking your own unit early, especially if the person being treated has young brothers or sisters.

Infusion day

The infusion itself is undramatic compared with everything around it. The cells go in through a drip. It is a single dose, though the dose may arrive as more than one bag, and every bag is given.

Each bag is thawed and then infused quickly, within twenty minutes of thawing. With preparation, checks and a period of monitoring afterwards, the day takes a few hours rather than a few minutes.

At least 48 hours must pass between the last dose of conditioning chemotherapy and the infusion, so there is usually a short gap between the hardest part and this one.

What the team watches for

The cells are frozen in a preservative called DMSO. Some people react to it, and reactions can occasionally be serious, so you are watched closely during and after the infusion. Paracetamol and an antihistamine are usually given beforehand as a precaution.

Settling in for a long stay

Transplant units suggest bringing things that make a small room feel like yours for a month or more: your own pillow and bedding, comfortable clothes, toiletries, and whatever occupies you, books, a tablet, headphones, something to make with your hands. Eye masks and ear plugs come up often, because hospitals are not quiet.

Whether a parent or partner can stay overnight is decided by each centre, and arrangements differ. Some units have rooms for parents next to the ward and charities provide free accommodation for families travelling a long way. Ask your own centre, it is one of the most practical questions you can settle early.

Questions you might take to your team

• How long do you expect the admission to be, for someone in my situation?

• What are your visiting rules, and do they change as counts recover?

• Can someone stay overnight with me, or with my child?

• What help is there for family travelling or staying nearby?

• What can I bring into the room, and what is not allowed?

• What happens on infusion day, hour by hour?