Monday, January 07, 2019

Pediatrics Study: LAIV Less Effective Against H1N1 Than Flu Shot

Credit CDC


The LAIV (Live Attenuated Influenza Vaccine) has had a rocky road the past few years, with ACIP (Advisory Committee for Immunization Practices) after reviewing two years of disappointing data - recommending against its use in the summer of 2016 (see  CDC Statement On ACIP Recommendation Against Use Of Inhaled (LAIV) Flu Vaccine). 
LAIV vaccines – unlike the standard flu shot - are delivered via a nasal spray, not a needle.  While only licensed for certain groups, it makes the flu vaccine far more accessible, particularly for those who hate shots.
Other countries, including Canada and the UK, continued to recommend its use while citing better data (see When Flu Vaccine Studies Collide). This past summer, after a reformulation of the FluMist (tm) vaccine, the CDC once again approved the LAIV for use in appropriate groups.
Live Attenuated Influenza Vaccine [LAIV] (The Nasal Spray Flu Vaccine)

For the 2018-2019 U.S. influenza season, CDC and its vaccines advisory committee (ACIP) recommend that providers use any licensed, age-appropriate influenza vaccine (Inactivated influenza vaccines (IIV), Recombinant influenza vaccine (RIV), or live attenuated influenza vaccine (LAIV4) with no preference expressed for one vaccine over another. (LAIV4 is again a recommended option for people for whom it i
s otherwise appropriate.) Learn more.

While again on the `approved' vaccine list for 2018, not everyone was enthused. In May of 2018 the American Academy of Pediatrics weighed in saying:
AAP: Give children IIV flu shot; use LAIV as last resort
Melissa Jenco, News Content Editor
Editor’s note: An updated story on AAP flu vaccine recommendations is available at

The Academy recommends pediatricians give children inactivated influenza vaccine in the upcoming season and use live attenuated vaccine only as a last resort.

(Continue . .  )

This year appears to be the first H1N1-centric flu North American season since 2015-16 - and with the LAIV back in play - a lot is riding on how well it protects against this subtype.

Against this contentious and at times confusing backdrop we have a new review of the VE (vaccine effectiveness) of the LAIV vs. the flu shot - published today in the journal Pediatrics - which once again finds the LAIV's past effectiveness against H1N1 seriously lacking.
January 2019
Live Attenuated and Inactivated Influenza Vaccine Effectiveness
Jessie R. Chung, Brendan Flannery, Christopher S. Ambrose, Rodolfo E. Bégué, Herve Caspard, Laurie DeMarcus, Ashley L. Fowlkes, Geeta Kersellius, Andrea Steffens, Alicia M. Fry, for the Influenza Clinical Investigation for Children Study Team, the Influenza Incidence Surveillance Project, the US Influenza Vaccine Effectiveness Network


BACKGROUND: Researchers in observational studies of vaccine effectiveness (VE) in which they compared quadrivalent live attenuated vaccine (LAIV4) and inactivated influenza vaccine (IIV) among children and adolescents have shown inconsistent results, and the studies have been limited by small samples.
METHODS: We combined data from 5 US studies from 2013–2014 through 2015–2016 to compare the VE of LAIV4 and IIV against medically attended, laboratory-confirmed influenza among patients aged 2 to 17 years by influenza season, subtype, age group, and prior vaccination status. The VE of IIV or LAIV4 was calculated as 100% × (1 − odds ratio), comparing the odds of vaccination among patients who were influenza-positive to patients who were influenza-negative from adjusted logistic regression models. Relative effectiveness was defined as the odds of influenza comparingLAIV4 and IIV recipients.
RESULTS: Of 17 173 patients aged 2 to 17 years, 4579 received IIV, 1979 received LAIV4, and 10 615 were unvaccinated. Against influenza A/H1N1pdm09, VE was 67% (95% confidence interval [CI]: 62% to 72%) for IIV and 20% (95% CI: −6% to 39%) for LAIV4.
Results were similar when stratified by vaccination in the previous season. LAIV4 recipients had significantly higher odds of influenza A/H1N1pdm09 compared with IIV recipients (odds ratio 2.66; 95% CI: 2.06 to 3.44). LAIV4 and IIV had similar effectiveness against influenza A/H3N2 and B. Our overall findings were consistent when stratified by influenza season and age group.

CONCLUSIONS: From this pooled individual patient–level data analysis, we found reduced effectiveness of LAIV4 against influenza A/H1N1pdm09 compared with IIV, which is consistent with published results from the individual studies included.

Essentially, the IIV (regular flu shot) was more than 3 times more effective against H1N1 than was the nasal mist in patients aged 2 to 17 years during the study period.
That said, these results are based on past flu seasons (2013-2016), and may not necessarily reflect how well the LAIV will perform this winter against the current H1N1 strain.
The full study is behind a paywall, as is an accompanying editorial (see Live Attenuated Influenza Vaccine: Will the Phoenix Rise Again?) by Pedro Piedra, MD, of Baylor College of Medicine in Houston.

Although we will get some preliminary data on the VE of this year's flu vaccines in the next month or so, it will probably be late spring or early summer before we get a good read on how well the reintroduced LAIV did against this year's H1N1 flu strain.

Stay tuned.

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