Racing could have been postponed for a "further period of at least a week" had stringent new vaccination requirements not been imposed, the British Horseracing Authority has said.
It was a condition of racing resuming following the enforced six-day shutdown due to equine flu that in order for a horse to fulfil an entry, it must have had the relevant vaccination within six months of the race in question. Any horse having a new vaccination cannot run for seven days.
That has led to a raft of complaints from some trainers, while others are not as badly affected.
Announcing additional opportunities for trainers needing to prepare horses for the upcoming spring festivals, the BHA said in a statement: "The BHA has today announced that it intends to schedule additional alternative races to assist trainers in their preparation for upcoming major festivals for horses that may miss out on essential prep or qualifying runs in the coming 10 days owing to the new vaccination requirements.
"The additional opportunities will be scheduled on or around the weekend of February 23, in order that horses which require vaccinations over the coming days will be eligible to run. Like all other British races, they will only be available to horses who have been vaccinated within the last six months.
"It was agreed that, if racing was to return, there should be stringent biosecurity measures put in place to protect the welfare of the breed and reduce the chance of further disruption.
"The sport is taking a measured risk by returning to racing this quickly, and for that risk to be deemed manageable then it was necessary that protective measures should be put in place.
"This includes the fact that horses that have not been vaccinated in the last six months should not be allowed to run. Put simply - without this we would not be racing. It could open the sport up to an unacceptable level of risk.
"The science is unequivocal that vaccines help reduce the effect and spread of equine influenza. This was a view that was stated by Dr Richard Newton - the Animal Health Trust's world-leading expert in this field - and supported unanimously by the experts on the veterinary committee."
The statement went on: "Trainers had been advised on January 25 that, due to the concerning situation in Europe where outbreaks have occurred in vaccinated horses, and an unprecedented number of cases in unvaccinated non-thoroughbreds in Britain, all horses which have not had a vaccination against equine influenza within the last six months should receive a booster vaccination.
"We appreciate that the six-day mandatory stand down period following vaccination, which is a welfare measure on behalf of the horse, will mean that some horses who were not subsequently vaccinated will not be able to run for a short period.
"However, to ensure a level playing field it would have been necessary to cancel all racing for a further period of at least a week."
It added: "The BHA is committed to the return to racing whilst minimising the risk of equine influenza spreading further within the sport, causing further disruption. This is our main priority.
"We recognised in making the decision last night that some participants could be disadvantaged and we are doing what we can to mitigate that without compromising the management of the outbreak."
Racecourses ready to roll
Musselburgh chief executive Bill Farnsworth is looking forward to "getting the show back on the road" as racing swings back into action on Wednesday.
The track has endured a trying few weeks, with the cold snap at the beginning of the month followed by the six-day shutdown due to an outbreak of equine flu scuppering the venue's high-profile Cheltenham Trials meeting.
With the British Horseracing Authority having now given the green light for Wednesday's cards, Farnsworth is thrilled the Edinburgh track will help the wheels start rolling once more.
He said: "We're just pleased to be back racing again.
"It's been a topsy-turvy few weeks. We lost our original Cheltenham Trials fixture, which was due to be our richest ever meeting, at the start of the month due to the weather. We then re-scheduled that meeting for last weekend, only to have that cancelled due to the equine flu outbreak.
"Tomorrow's fixture isn't actually our fixture - we acquired it a few weeks ago from Towcester, because no one else was really in a position to race, so we stepped in.
"As we were viewing that as a bonus meeting, we decided not to charge for entry - so we're delighted to be getting the show back on the road, and with free entry."
Plumpton's clerk of the course Mark Cornford is similarly relieved that racing is back on the agenda - because the Sussex track was another to feel the bite of the cold weather.
He said: "We're delighted to be one of the first courses to race.
"We actually lost our last meeting due to the weather, so we're thrilled we're not going to lose another to circumstances beyond our control.
"We have done a thorough clean of the stable yard and all the other relevant areas. The boxes are fogged - which is like disinfectant - before every meeting, and they were done for our last meeting and have been done again by circumstance.
"We'll have hand sanitisers available in the stable yard for people to use if they wish, the veterinary team will be on the course to monitor horses coming off the lorries, generally check they're in good health and check all the paperwork we need to see.
"It's a lot of commonsense measures, and we're just happy to be racing."
Kempton also race on Wednesday, and clerk of the course Brian Clifford believes the six-day blank spell was in the best interests of the sport.
He said: "It's great racing is back on.
"I think it (the shutdown) was the right thing to do, to take some time to see how the situation unfolded, but it's great we're back in action.
"We have carried out a level-two clean of the stables, the unsaddling boxes, the starting stalls - we have done everything we possibly can on that front."
Southwell also race on Wednesday, although all cards are subject to strict biosecurity measures - including a declaration form confirming there have been no symptoms of flu and that a temperature check has been completed.
Only that, together with a horse passport showing an inoculation from within six months of the race meeting, will allow horses to be unloaded at a racecourse.