What states like Massachusetts are doing is making sure that people can continue to get COVID vaccines at the most convenient location, which for most people is their local pharmacy, says Neil Maniar, director of Northeasterns master of public health program

Brain function: Brain fog, memory problems, cognitive impairment, insomnia, headaches (especially migraine), behavioural changes, learning problems, nominal aphasia Mood: Mood swings, irritability, depression, anxiety, hallucinations, delusions, psychosis Sensory: Peripheral paraesthesia (pins and needles), numbness, neuropathic pains, poor balance, reduced vibration sense or proprioception (joint position sense), tinnitus, ataxia, taste impairment, sometimes myelopathy Constitutional: Fatigue, anaemia (either macrocytic, or normocytic when also iron deficient or associated with thalassaemia minor), other cytopenia, abdominal complaints, malabsorption, failure to thrive, weight loss, diarrhoea, hyperpigmentation, glossitis, (aphthous) stomatitis, infertility, urinary tract infections Motor: Muscle weakness, altered reflexes (increased in degeneration of the spinal cord, reduced when peripheral neuropathy dominates), spasticity, seizures, cardiomyopathy Autonomic: Urinary and/or faecal incontinence, postural hypotension or dizziness, erectile dysfunction Diagnosing B 12 deficiency can be challenging because no single specific measurement exists to reliably diagnose or refute the presence of B 12 deficiency 11 12 26 27 (box 2)

If you are experiencing symptoms that might suggest a deficiency in either vitamin, it is essential to consult your GP for appropriate blood tests rather than self-treating with supplements
They will probably only be necessary if the information you get from the blood tests is confusing or unclear