The letter says effective plans for the 2020/21 flu season are 'more important than ever' to protect those at risk and reduce pressure on the NHS and social care in light of the COVID-19 pandemic.
It warns that this winter could see flu and COVID-19 circulating at the same time and that concerns about COVID-19 may increase demand for flu vaccination.
The letter says: 'In light of COVID-19, we ask primary care providers (GP practices and community pharmacies) to urgently review your vaccine orders now to make sure the number of vaccines ordered meet at least national ambitions and previous uptakes rates, whichever is highest.'
The letter adds that discussions are underway about expanding the flu programme for 2020/21, and that GPs will be advised of any changes 'in due course'.
For the time being, flu jabs under the national vaccination programme will cover children aged two to 10, those aged six months to under 65 years in clinical risk groups, pregnant women, people over 65, care home residents, carers, close contacts of immunocompromised individuals and health and social care staff.
The letter acknowledges that delivering the flu vaccination programme in 2020/21 is likely to be more difficult because of the impact of COVID-19 on health and social care services.
'We understand that planning this year is more challenging with the uncertainties of staff absences, and how long policies around social distancing and school closures will remain in place. However, it is more important than ever to make every effort to deliver flu vaccination,' the letter says.
'Those most at risk from flu are also most vulnerable to COVID-19. We must do all we can to help protect them this winter.'
The letter advises GP practices to continue to plan for the flu programme 'as usual', with a view to completing vaccinations by the end of November.
The letter adds that NHS officials 'expect universal vaccination of health and care workers', and says further guidance on this will be published in due course.