2019-20 flu vaccine recommendations

The CDC just published their recommendations for the 2019-20 flu vaccine (see https://www.cdc.gov/mmwr/volumes/68/rr/rr6803a1.htm?s_cid=rr6803a1_w%20CDC%20Offers%20Vaccine%20Recommendations%20for%202019%E2%80%9320%20Flu%20Season )

Details:
--flu vaccine is recommended for all persons >6 mo old
--trivalent influenza vaccines:  hemagglutinins (HA) derived from an A/Brisbane/02/2018 (H1N1)pdm09–like virus, an A/Kansas/14/2017 (H3N2)–like virus, and a B/Colorado/06/2017–like virus (Victoria lineage)
--quadrivalent influenza vaccines: as with trivalent but additional hemagglutinin derived from influenza B vaccine virus, a B/Phuket/3073/2013–like virus (Yamagata lineage)
--flu vaccines do work, though somewhat variably from season to season (some vaccines have better actual virus matches than others). But overall, the CDC estimates that from 2010-11 through 2015-6, the vaccine prevented per season:
    --1.6-6.8 million illnesses
    --790,000 to 3.1 million outpatient medical visits
    --39,000 to 87,000 hospitalizations
    --3,000 to 10,000 respiratory and circulatory deaths
--timing of vaccination: as in past years, the CDC is balancing the unpredictability of the onset time of the flu season with concerns of waning immunity from the vaccine (see blog below), deciding that the vaccine should be offered in late October (though kids 6 mo to 8yrs who need 2 doses of vaccine should get the first one as soon as possible, since the second one needs to be at least 4 weeks later, more below)
    --in 75% of the 36 flu seasons from 1982-83 through 2017-8, peak influenza activity was in February or later
    --though, despite  waning immunity, they do not recommend revaccination later in the season
    --and, there are pretty commonly more than one outbreak in a community in a season, and a “tail” to the season, where there are lingering new cases many months after the peak

Specific populations/situations:
--those at higher risk for medical complications with flu:
    --children 6-59 months
    --all >50yo
    --those with chronic pulmonary (including asthma), cardiovascular (except isolated hypertension), renal, hepatic, neurologic, hematologic, or metabolic disorders (including diabetes)
    --immunocompromised, including immunosuppression from meds and HIV
    --women who are or will become pregrant during the flu season
    --children (6mo-18yo) on aspirin/salicylates
    --residents of longterm care facilities
    --American Indians/Alaska Natives
    --people with BMI>40
--health care personnel, broadly defined. Including volunteers, nonclinical people in health facilities, household contacts and caregivers of those <5yo , >50yo, or those with the above high-risk medical conditions

Specific patient groups:
--children 6 mo through 8 years:
    --those 6-35 months: 0.25 ml Afluria Quadrivalent vaccine; 0.5ml Fluarix Quadrivalent; 0.5ml FluLaval Quadrivalent;  or Fluzone (either 2.5 or 5 ml, depending on the concentration)
    --LAIV4 (the live attenuated vaccine):  0.2ml intranasally if >2 yo
    --if <9yo, need 2 doses during first season of vaccination (though not if they have received 2 doses before, even if not in the same season)
--pregnant women: all who are pregnant, might be pregnant or postpartum should get the flu shot, though not the LAIV4, and the vaccine can be given at any time during the pregnancy
--those >65yo: the high-dose vaccines have superior efficacy against laboratory-confirmed influenza
--immunocompromised: not use live virus vaccines (LAIV), based on general concerns about getting disease from the live organisms, though no real data on this.
--history of egg allergy:  those with allergic reactions more than just urticaria should be watched closely after getting the vaccine [though RIV-4 (Flublock Quadrivalent, licensed for those >18yo) and ccIIV4 (Flucelvax Quadrivalent, licensed for >4yo) are not prepared in embryonated eggs]
--antiviral influenza meds: may decrease effectiveness of LAIV if given vaccine 2-14 days before
--administration with other vaccines: inactivated vaccines can be given with other ones, though best at separate anatomical sites; LAIV can be administered at same time as other live vaccines; but if live vaccine already given, need to wait 4 weeks for another one
    --of note, several studies have found decreased antibody response to some vaccines, including PCV13, tetanus, pertussis when given together with flu vaccine; but unclear what the clinical significance of this is
    --kids 6-23 months getting flu shots with PCV13 have increased risk of fever that day and the next; and increased risk of febrile seizures if given with PCV-13, or DTaP, as has been found in some prior years

--for the different vaccines: see Table 1 in https://www.cdc.gov/mmwr/volumes/68/rr/rr6803a1.htm?s_cid=rr6803a1_w%20CDC%20Offers%20Vaccine%20Recommendations%20for%202019%E2%80%9320%20Flu%20Season ;

--Table 2 has the contraindications/precautions with the different flu vaccines
--Table 3 has the different inactivated flu vaccines for kids

so, a few issues:
--there is certainly significant morbidity and mortality associated with influenza, esp in the young/old/infirmed. And both the incidence and severity of the illness can be decreased dramatically by routine vaccination
--there are important social concerns about vaccination, especially that younger people seem to be more protected by vaccination, and, if not vaccinated, they are often the vectors carrying the virus to these more susceptible people
--other concerns for younger/working people is the large burden on their lives: missed school and work
--the CDC does comment, as in years past, that in general it is best to wait until late October to start giving the vaccine (though in Boston, the vaccine is available well before that; and it is advertised pretty aggressively by pharmacies as soon as it is available!!).  See below on the significant data suggesting that the vaccine effectiveness seems to decrease significantly over even a few months. The high-dose ones used in those >65yo do elicit a higher immune response and clinical benefit (important because these people do have lower immunological  and clinical response to the usual dose vaccines), but I have not seen any studies assessing immune response or clinical effectiveness of these high-dose vaccines over time.
    --there often is a “tail” to the flu season, extending into the early Spring, so the protection at that point is likely much less
    --it is usual that in many areas (such as Boston), the virus has appeared in other areas of the country first, so there is time to immunize (it takes about 2 weeks to get an adequate immune response). And we can use the various antiviral influenza meds for prevention, if the virus appears sooner than expected
   --BUT, it is very important that people be protected. So, one might consider waiting a longer time to immunize if the patient comes for care frequently and reliably, or there is a home care nurse or provider who can administer the shots on short notice. Best to have systems where these patients can be identified easily and outreach done if they have not been immunized

http://gmodestmedblogs.blogspot.com/2017/08/should-we-delay-giving-flu-vaccine.html comments on the waning effectiveness of flu vaccines over time, noting about a 10% decrease in vaccine effectiveness per month (maximum effectiveness was 14 days after immunization, dramatically decreasing by 4 months later)
http://gmodestmedblogs.blogspot.com/2018/10/80000-died-in-2017-18-flu-epidemic-in-us.html has the CDC report of the 2017-18 flu season estimating the US death rate from the flu being 80,000 (I have been quite successful using this number to convince patients historically resistant to getting flu shots to start)
http://gmodestmedblogs.blogspot.com/2018/01/flu-vaccine-in-older-people-decreased.html , a blog suggesting that annual flu shots in the elderly over several years had increased clinical effectiveness
http://gmodestmedblogs.blogspot.com/2017/12/global-deaths-from-influenza.html , with more recent estimates of the very high global death rates from flu

geoff​

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