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Individual FAQs

Frequently asked questions about Flu and Flu Vaccines

Vaccine Information FAQs
  • Is it safe for me to have two flu vaccinations in one season?

    Receiving two flu jabs of standard strength is more protective but if given days apart are not likely to be more harmful.

  • What strains does the seasonal flu vaccine protect against?

    Each flu season, all vaccines are prepared to the latest WHO specifications;

    It is recommended that the vaccines for use in the 2019-2020 influenza season (northern hemisphere winter) contain the following:

    • A/Brisbane/02/2018 (H1N1)pdm09-like virus;
    • A/Kansas/14/2017 (H3N2)-like virus; *
    • B/Colorado/06/2017-like virus (B/Victoria/2/87 lineage);
    • B/Phuket/3073/2013-like virus (B/Yamagata/16/88 lineage).

      It is recommended that the influenza B virus component of trivalent vaccines for use in the 2019-2020 northern hemisphere influenza season be a B/Colorado/06/2017-like virus of the B/Victoria/2/87-lineage.
      * The A(H3N2) component was recommended on 21 March 2019.

    You can find the full WHO flu vaccination strain specifications here

  • How long does flu vaccine take to work?

    About 2-3 weeks.

  • How effective is the vaccine? – If I have a flu jab, can I still get the flu?

    Flu vaccinations are 70-80% effective, provided that there is a good match between the strains used to make the vaccine, and the strains of flu that are going around. There are very sophisticated systems in place for monitoring strains of flu around the world, so it is increasingly possible to predict which strains are most likely to cause trouble. Protection is excellent against the strains from which the vaccine is made, and even if you catch the flu, the illness will almost certainly be milder than if you had not been vaccinated.

  • How long does the flu jab last for?

    About 6-12 months. The vaccine protects against different strains, and the protection against some of the strains may last longer than others. Longer lasting flu vaccines are currently at a research stage.

  • When is the best time to be vaccinated?

    The best time to be vaccinated is between late September and December, ready for the winter. If you wait until there is a flu epidemic in progress, it may not otherwise be possible for you to get good protection quickly enough.

  • How can I find out more about flu and flu vaccinations?

    If you have specific questions about you own medical history and circumstances, we’ll do our best to help when you come in for your jab. For general information, see our links page.

  • Does infection with flu give me immunity?

    Only to the particular strain of flu that caused the infection. The virus changes over time, and new strains appear. Protection from past infection or previous vaccination is unreliable – the most effective way of increasing your protection is to be vaccinated every year.

  • What are the benefits of flu vaccinations? – Should I bother?

    The benefits of vaccination to healthy, working adults and their employers are well-established: vaccination cuts the risk of ‘flu by approximately 70-80%, and reduces time off work from colds and flu by forty three per cent. Each winter, up to one third of British adults may suffer from flu, and one third of sufferers become ill enough to visit their doctor. For companies and organizations, the potential benefits are even greater than the benefits to the individual: respiratory viruses can spread easily within any large group of people, working together and sharing facilities on the same site. It is to everyone’s advantage that as many people as possible within the same organization should be protected.

  • Will the new seasonal flu jab protect me against swine flu?

    This year’s Northern Hemisphere and Southern Hemisphere flu vaccines both include protection against H1N1 swine flu.

  • What exactly is flu anyway?

    The commonest symptoms are: rapid onset of fever, shivering, headache, muscle aches, and a cough. Flu causes a much more severe illness than the common cold: a cold doesn’t cause fever or muscle aches. People with flu can feel very ill indeed, often resulting in several days of being confined to bed. Most people recover easily, but would have much preferred to avoid the experience altogether, which is where flu vaccine comes in. For some victims, flu can cause more serious complications, like bronchitis and pneumonia – potentially life-threatening in the elderly, asthmatics and those with pre-existing medical conditions.

Special Requirement FAQs
  • Will the effectiveness of the flu vaccine be reduced by the use of statins?

    A recently published study looked at flu-related illnesses in older people who had been vaccinated against flu, and compared the rate of infection in those who were taking statins with those who were not. They found a slightly increased rate of infection among the group taking statins, which suggests that vaccination was slightly less effective in that group. More research is needed to investigate the reasons for this, and what can be done to overcome them (such as changing the vaccine dose for older patients – already a feature of some more specialised flu vaccines for older people).

    Flu vaccination remains an important protective measure, and it is vital not to lose out on protection in the meantime.


  • Can I be vaccinated if I have a cold?

    There’s no problem being vaccinated when you or your child have a cold or a minor illness. However, we prefer not to vaccinate people who currently have a fever, since the immune response to the vaccine may not be as good; it is better to defer vaccination until your fever has resolved.

  • I am allergic to eggs – can I still have the flu jab?

    Well-documented, severe allergy means that you should not be vaccinated using vaccine produced in eggs. True egg allergy is very rare: we will usually vaccinate people who report no problem eating egg products such as cakes or egg pasta. If you are uncertain, talk things over with your doctor, or with the doctor or nurse giving the vaccine as we do have egg-free cell-based vaccines available for the 2019/2020 season.

  • Will the flu vaccine react with any medication?

    Please tell the doctor or nurse giving the vaccine about any important aspects of your medical history, and about any medication you are taking. Flu vaccine does not interact with any other vaccine or medication. However, any treatment that might reduce your immunity can reduce the effectiveness of the immune response. Vaccination can briefly affect the results of certain types of blood tests (serology tests), so if you have a blood test within a few days of being vaccinated, please ask the person taking the blood sample to mention your flu jab on the laboratory form.

Concerns or Queries FAQs:
  • What are my chances of having an anaphylactic reaction after having the flu vaccination?

    True anaphylactic reactions with vaccinations are exceedingly rare, sudden death from anaphylaxis even more so. Any site offering vaccinations should be equipped with drugs that are effective treatments against anaphylaxis and have staff onsite trained to administer and monitor patients if a reaction were to occur. The vaccines may contain some components that cause allergic reactions, such as egg but in such small quantities that it would be unlikely to happen for the first time during a flu vaccination. Everyone who attends for a flu jab is asked a series of screening questions to ensure that it is safe to administer the vaccine.

  • Can flu vaccine cause flu?

    Injected flu vaccine cannot cause infection because it doesn’t contain live virus.

    The nasal spray vaccine given to children contains a specially modified (“cold-adapted”) live virus that cannot survive at normal body temperature and is therefore incapable of causing infection.


  • Do any of your flu vaccines contain mercury / thimerosal / thiomersal?

    No, none of this year’s flu vaccines contain mercury-based preservatives.

  • Does the flu vaccine have any side effects?

    Flu vaccines are very safe. The commonest problem after vaccination is slight soreness of the arm at the point where the injection was given; and less often, slight temperature and aching muscles can occur for a couple of days, but this responds easily to remedies like paracetamol; or redness and irritation at the injection site, sometimes lasting 2 or 3 days – it responds to taking ibuprofen and applying a cold flannel. The risk of more serious reactions is extremely small – of the order of one in a million, or less; and considerably smaller than the risk of serious complications from the illness itself.

  • I have had the swine flu vaccine in the past. Do I need a seasonal flu jab this year?

     The H1N1 pandemic vaccine only protected against H1N1 flu, and it is uncertain how long that protection lasts. This year’s seasonal flu vaccine protects against three strains including H1N1, and therefore gives worthwhile additional protection.

  • I’m worried the H1N1 component of the flu jab will increase the rick of side effects. Is this true?

    Don’t be worried. At the start of the H1N1 swine flu pandemic, the first vaccines had to be manufactured very quickly, and contained additives (called adjuvants) to enhance the immune response. Many people who received those vaccines did experience a high rate of minor side effects – but these were caused by the adjuvants, and had nothing to do with the H1N1 component. Seasonal flu vaccines DO NOT contain these adjuvants. Seasonal flu vaccines protecting against H1N1 have not been linked to any increase in the rate of side effects.

  • I’ve never had a flu jab before – and I never had the flu. Why should I be vaccinated now?

    Past success in avoiding flu won’t guarantee you’ll be protected in future. It’s up to you to choose between playing the odds and taking a positive step to protect yourself.

  • Why does my employer offer free flu jabs?

    Flu vaccination successfully reduces illness during the winter, and the illness can sometimes be very serious. In the UK, attitudes to flu are muddled by the fact that the vaccine is usually only offered free to people in designated “high-risk” categories – usually people at special risk from complications (check with your GP to see if you are entitled to free vaccination). In other countries, the situation is different. In the USA, for example, annual vaccination for healthy working adults is very much a routine, and is widely regarded as an important health benefit. Key workers, highly paid staff, those working in direct contact with the general public or in public places, staff in large open plan offices (i.e. sharing the same air) and staff who simply have caring employers, are among those generally offered free vaccination in the workplace. While there is certainly a benefit to employers in helping staff stay healthy, flu vaccination protects your leisure time and your family as well, and not just your ability to work. Don’t forget, the flu season begins at Christmas, and ends around the Easter break.

Aftercare FAQs:
Lifestyle FAQs:
  • Are flu vaccines Kosher (or Halal, which follows similar principles)?

    We would always advise you to seek appropriate religious advice, but the following facts may help inform this for you.


    Vaccines are made from viruses that are grown in culture (in order to yield sufficient quantity to turn into vaccines). All flu viruses need mammalian cells in which to grow. The standard flu vaccine production method is to inoculate “seed” virus into embryonated (i.e. fertilised) hens’ eggs. Hens are kosher animals, and hens’ eggs are kosher. The situation regarding embryonated hens’ eggs might be a little more complicated, but these should be kosher also – Jewish law permits eating eggs found inside a chicken, and these may well be fertilised or embryonated.

    We do vaccinate a great many observant Jewish and Muslim patients, who have never found themselves in difficulty about this aspect of the vaccine.

    Other points to consider:

    1. Having grown in culture, the virus particles are extracted, killed and purified, so it is very doubtful how much actual egg material remains in the vaccine – only a trace at most.
    2. Jewish law specifically permits anything to be done in the cause of saving a life, and the flu vaccine is certainly in this category.

    Fluenz – the live vaccine currently offered to children – contains traces of modified pork gelatin, and therefore raises concerns about acceptability to observant Muslims and Jews, especially given that alternatives are available.

    Jewish religious authorities have however concluded that Fluenz should be regarded as Kosher, since it is administered by the nose, is modified from its original form, and provides an important benefit to health.

    Furthermore, kosher principles are considered to apply to dietary laws and eating, not injection or inhalation for medical rather than nutritional purposes.

  • Can I drink alcohol after the flu vaccination?

    It is considered sensible to avoid alcohol for several hours, but this is not an absolute rule: if you must drink, drink moderately.

  • Do you recommend the flu vaccine if travelling abroad?

    Yes, protection against seasonal flu is definitely a sensible precaution for travellers. Additional risks for travellers include a higher risk of transmission of airborne respiratory infection during flights, and well-documented outbreaks of flu on cruise ships, so flu vaccination is a precaution that is well worth taking. Keep in mind that in tropical countries, flu is not seasonal and the risk is year-round.

  • I am a blood donor. If I have a flu jab, will it be OK for me to donate blood?

    Adult flu vaccines are “killed” vaccines. The National Blood Service does not require any delay between vaccination and blood donation, for this category of vaccine, so there’s no problem. The National Blood Service Helpline is 0300 123 23 23

  • I live far away. Can you send me a dose of vaccine?

    No, sorry. In special cases (such as when certain types of vaccine are in limited supply), we sometimes do allow individual patients who attend the practice in person, to take away vaccine doses for family members. If you would like this to be considered, you would need approval from your local GP practice, and you would have to put us in direct touch with them so we can confirm they are happy to administer the vaccine for you.

  • I’m a strict vegetarian, is it OK for me to have the vaccine?

    The vaccine production process includes culture in embryonated hens’ eggs. Only a trace of egg protein remains in the vaccine, but some strict vegetarians may object to this. If you have religious reasons for avoiding eggs, you should take appropriate religious advice.

Motherhood FAQs:
Children FAQs:
  • Are there any children who aren’t suitable for the nasal spray flu vaccine?

    The nasal flu vaccine may not be suitable for a small number of children, who have the following conditions:

    • severe asthma (children with mild or moderate asthma are able to have the flu nasal spray)
    • active wheezing at the time of vaccination
    • a severely weakened immune system
    • an egg allergy

    These children are still able to be vaccinated using the intramuscular vaccine.

  • Can my children have the flu vaccine?

    Yes. There’s no reason not to vaccinate children, and plenty of benefit. Apart from protecting their own health, vaccinating children also reduces household and community spread of flu.

    Children who have not been vaccinated previously generally need a second dose of vaccine 4 weeks after the first, for full effect.

    Children can be vaccinated from the age of six months.

  • How is the Fleet Street Clinic able to vaccinate children when a lot of pharmacies and other practices can only vaccinate over 18 year olds?

    All our vaccines are administered by doctors or nurses, fully trained and experienced in vaccinating children – not by pharmacists or other health professionals.

  • How many doses of Fluenz should my child have?

    We are currently offering two doses of Fluenz to all children aged between 2 and 9 – these are given four weeks apart. If you have been offered only a single dose for your child, under the NHS, we would be happy to provide a further dose, if you would like us to.

  • I have small children. Is there any danger of passing infection to them, if I have a flu jab myself?

    No. The injected flu vaccine does not contain live virus.

  • Is it OK for my child to have a flu jab at the same time as (or soon before or after) other vaccines?

     Timing issues mainly apply to live vaccines like MMR, chickenpox (varicella) and BCG, which should generally either be given on the same day as each other, or with at least a 4-week gap. These issues don’t apply to injected flu vaccines, which are “killed” vaccines. However, they may theoretically apply to the use of FLUENZ, the nasally administered vaccine which is currently being offered to children. Do tell the doctor or nurse about any vaccines that are likely to be due, or have recently been given, so that we can give you the best advice.

  • Is it possible to overload the immune system by giving too many vaccines to children?

    From birth, babies’ immune systems protect them from the germs that surround them. Without this protection, babies would not be able to cope with the tens of thousands of bacteria and viruses that cover their skin, nose, throat and intestines. Vaccines are designed to strengthen a baby’s immune system and protect them from very serious diseases. There is no evidence that any vaccine programme “overloads” a child’s immune system. In the US, where more vaccines are given in a single GP visit than in the UK, a study (Offit et al, 2002) found no difference in hospital admissions among children who had had multiple immunisations compared with children who had had only polio vaccine. In theory, a baby could response safely and effectively to around 10,000 vaccines at any one time (Offit et al, 2002). So a baby’s immune system can and does easily cope with the addition of multiple doses of vaccine to the immunisation programme.

  • What is the youngest age at which a baby can be vaccinated against flu?

    In the UK as well as most other countries, flu vaccines are only licensed for use in babies aged over 6 months. The main concerns are not about harm, but about effectiveness. However, a study in the United States of 1375 infants aged just 6-12 weeks confirmed that flu vaccine was safe and effective in this age group also, and therefore might be considered under special circumstances. Vaccinating mothers in pregnancy also passes immunity to the newborn baby, and is one of the reasons why this is recommended.

  • Why are children recommended to have a booster flu vaccination?

    Children under 9 years of age who have not been vaccinated previously are recommended to receive a booster 4 weeks after the initial flu vaccination. The booster dose is needed for young children to produce a protective immune response.

    Going forward, in subsequent years, they will only need a single annual dose.

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