England's chief pharmaceutical officer has admitted local pharmacies may have shortages of some antibiotics to treat Strep A infections.
But David Webb also said that on a national level, there were "sufficient" stocks as he tried to reassure parents worried about the current outbreak.
Pharmacists have complained of a lack of antibiotics, including the liquid version of penicillin, which is often given to children.
Mr Webb's comments came as the number of youngsters under 15 who have died after contracting Strep A in the UK rose to 15, according to the UK Health Security Agency (UKHSA).
New data for England shows the number of deaths since September has increased to 13.
The other two fatalities were recorded in Wales and Northern Ireland.
Illnesses caused by Strep A include scarlet fever, strep throat, and the skin infection impetigo.
Though most infections are mild, the bacteria can evolve into a life-threatening illness called invasive Group A Streptococcal disease.
The National Pharmacy Association has pointed to "blips" in the supply chain of liquid penicillin, while the Association of Independent Multiple Pharmacies said pharmacists were struggling to get hold of all they needed.
Pharmacy director Zeshan Rehmani criticised the Department of Health for being "out of touch" after it mooted proposals to give antibiotics to children in schools to help fend off illnesses including Strep A - telling Sky News: "There's no drugs. Today, we haven't been able to get any penicillin in stock at all."
But chief pharmaceutical officer for NHS England, David Webb, said: "Local pharmacy teams may be experiencing a temporary interruption of supply of some relevant antibiotics due to increased demand. On a national level, sufficient stock exists for the NHS."
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A Health Department spokesperson said there was no "supplier shortage" of antibiotics to treat Strep A, but admitted there were "sometimes surges for products - and increased demand means some pharmacies are having difficulties obtaining certain antibiotics".
A statement added: "We are working urgently with manufactures and wholesalers to explore what can be done to expedite deliveries and bring forward stock they have to help ensure it gets to where it's needed, to meet demand as quickly as possible and support access to these vital medicines."
No evidence of new strain
Since September, the UKHSA said there had been 652 reports of the invasive form of the disease, which is higher than during the same period over the last five years.
In the current season of Strep A infections, there have been 85 cases in children aged one to four.
That compares to 194 infections in that age group across the whole of the last high season in 2017/2018.
There have also been 60 cases in children aged five to nine. Since September, 60 deaths have been reported across all age groups in England.
The rise in infections is thought to be because of large amounts of bacteria and increased social mixing, the UKHSA added.
There is no current evidence that a new strain is circulating, the agency said.
"There are lots of winter bugs circulating that can make your child feel unwell, that mostly aren't cause for alarm," said the deputy director of the UKHSA, Dr Colin Brown.
"However, make sure you talk to a health professional if your child is getting worse after a bout of scarlet fever, a sore throat or respiratory infection - look out for signs such as a fever that won't go down, dehydration, extreme tiredness and difficulty breathing."