NHS England says orders should only be placed to cover a shortfall in vaccine supplies for NHS eligible patients or frontline social care workers.
It says: 'Further instruction on timing of extension of eligibility to all 50- to 64-year-olds will follow and stock should not be ordered for this cohort at this stage.'
Government guidance indicates practices can order between 150 and 1,000 doses of the Seqirus vaccines, and between 30 and 1,000 doses of the Mylan vaccine.
Practices with provisional orders with Sanofi for its egg-based quadrivalent vaccine should contact the supplier to confirm before placing a further order, NHS England says.
The government's vaccine stockpile will also include 2.15m doses of Flublok - a vaccine used in the US since 2016 which has been granted temporary authorisation in the UK by the MHRA.
The MHRA's assessment was based in part on evidence from another 'closely related' Sanofi flu vaccine, Supemtek, which was recommended for approval by the European Medicines Agency in September 2020. The MHRA said its assessment showed the two products are 'fundamentally similar' in terms of 'manufacture, control, quality, non-clinical and clinical evaluation'.
Deputy CMO Professor Jonathan Van Tam said: 'Flublok has been in regular use in the United States - and the evidence shows that it is an excellent product. I want to reassure everyone that all vaccines have undergone robust clinical trials and rigorous checks by the regulator to ensure they are safe, effective and of a high quality.'
More than 10m doses of flu vaccine are believed to have been delivered to providers across the UK to date.