Image supplied by Aintree Racecourse

Nicky Henderson has withdrawn a number of high profile horses from weekend engagements because they do not meet the vaccination criteria set out by the British Horseracing Authority in its decision to resume racing following the equine influenza outbreak.

The BHA announced late on Monday that racing would start up again, but with strict biosecurity controls in place and no entries or declarations will be accepted from horses that have not been vaccinated in the previous six months.

That rules out Santini, who was set to contest the Reynoldstown Novices’ Chase at Ascot on Saturday, while Christmas Hurdle heroine Verdana Blue cannot take up her entry in a fast-track qualifier for All-Weather Championships Finals Day at Kempton.

Henderson told Press Association Sport: “It’s been a frustrating two weeks, as we were snowed in before this. Obviously we are all delighted with the news, as this is what we wanted to hear after everyone had looked at the situation.

“We are only just getting our results back, but I gather they are all OK. We have still got some more to come, but I imagine they will be all right.

“We have got one or two frustrations because of the vaccinations — it has caught out one or two horses as they have just fallen outside of the window. We have just got to juggle a few things around, which is frustrating.

“Everyone uses different vaccination programmes. A certain percentage will be fine, but others won’t.”

Under the rules set out, no horses will be able to run until seven days after being given a vaccination.

Henderson added: “There are a few that were due to run this weekend that can’t run like Santini, and Verdana Blue can’t run in her fast-track qualifier, so that takes her out of her Good Friday race.

“Yellow Dockets can’t run in the Grade Two at Sandown and Beware The Bear is another who can’t run in the Grand National Trial at Haydock, but we could reroute him to the Eider Chase.

“We have just got to get our heads round a few things. We can sort them out today and they would be able to run next week, but that it is no good for many of them as for some these were the only races they could run in.

“You only have 10 positives tests (for equine flue) compared to all the negatives and with the percentages you had to go (resume racing) now.

“I do believe it was vital to start racing now otherwise you were never going to.”

The Seven Barrows trainer also confirmed via his Twitter feed that Top Notch would not be in action at Ascot.