8/10/2019 Infections PBL Part 2

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Mrs T is still a little confused as her father has had the flu vaccine already and iswondering why would her father still develop influenza? She wonders whether the flu vaccine caused him to have flu and why would the GP not write a prescription for her Dad or herself?

4. Why would a patient develop influenza despite having received the flu vaccine?

The actual efficacy of the influenza vaccination varies greatly year on year [1].One factor in the efficacy of the vaccine is the age and general health of therecipient [1]. A recent study in the United States found that influenza vaccineshave the lowest efficacy in patients aged 65 years and older [2]. As the immunesystem deteriorates as patients age, the level of protection afforded by thevaccine diminishes [1].

The second potential reason for developing flu despite having received thevaccine is the patient coming into contact with a strain of influenza virus that thevaccine provides no immunity from [1].

What is the purpose of using an influenza vaccine, if the patient may still developinfluenza?

Although there is still a chance the patient will develop flu, the disease itself isvery serious and can in fact be lethal.

Can the influenza vaccine cause flu? Provide reason.

No, though it is possible for people who have just had the flu vaccine to developflu-like symptoms. The reasons for this include an infection occurring caused byother respiratory viruses with symptoms similar to influenza, infection byinfluenza shortly before being vaccinated against it or during the period shortlyafter being vaccinated, or infection by a strain of influenza that the vaccineprovides no protection for [3].

Which patient groups should be receiving flu vaccines?

Already answered.

5. What is the scientific reasoning behind having another flu vaccine every yearwhen for most other preventative vaccinations there is no need to top up?

The vaccination (in healthy patients) lasts at least one influenza season [5]. Afterthis, the protection granted by the vaccine diminishes. In older patients, due to adecreased response to the vaccine, protection may not last for the whole year[4].Also, new vaccines are developed each year to protect against the strains of

influenza that are circulating.

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6. How is influenza transmitted?

Which simple measures can be used to avoid transmission?

Already answered.

References:

[1] http://www.cdc.gov/flu/about/qa/vaccineeffect.htm

[2] McLean, HQ. et al. (2014). Influenza Vaccine Effectiveness in the UnitedStates During 201213: Variable Protection by Age and Virus Type. The Journalof Infectious Diseases Advance Access.

http://jid.oxfordjournals.org/content/early/2014/11/18/infdis.jiu647.long

[3] http://www.cdc.gov/flu/about/qa/misconceptions.htm

[4] PHE (2014) Immunisation against infectious disease - "The Green Book".Chapter 19 - Influenza. Public Health England. www.dh.gov.uk

[5] http://www.cdc.gov/flu/protect/keyfacts.htm

http://jid.oxfordjournals.org/content/early/2014/11/18/infdis.jiu647.longhttp://jid.oxfordjournals.org/content/early/2014/11/18/infdis.jiu647.longhttp://jid.oxfordjournals.org/content/early/2014/11/18/infdis.jiu647.long