Protective efficacy of combined live intranasal and inactivated influenza A virus vaccines in the elderly.
OBJECTIVE
To evaluate the efficacy of adding intranasal live attenuated cold-adapted influenza A vaccine to inactivated influenza vaccine to prevent influenza A in elderly residents of long-term-care institutions.


METHODS
Randomized, double-blind, placebo-controlled study conducted over 3 years.


METHODS
Three large nursing homes.


METHODS
A total of 523 residents of nursing homes (mean age, 84.2 years).


METHODS
All participants received trivalent inactivated influenza vaccine parenterally and were randomly assigned to receive either live attenuated influenza A (H3N2) virus vaccine or placebo intranasally.


METHODS
Laboratory-documented influenza A was defined as a respiratory illness plus isolation of influenza A virus from nasal secretions, significant serologic response, or both. Participants were considered to have been exposed to influenza A if they resided in an institution in which cases of influenza A were documented. Outbreak-associated illnesses were defined as those occurring between the first and last isolation of influenza virus from within the institution, +/- 3 days.


RESULTS
Participants who received intranasal vaccine and were subsequently exposed to influenza A had significantly lower rates of laboratory-documented influenza A (9 of 162 vaccine recipients compared with 24 of 169 placebo recipients; vaccine protective efficacy, 60.6%; 95% CI, 18% to 82%), outbreak-associated respiratory illnesses (13 of 162 vaccine recipients compared with 34 of 169 placebo recipients; vaccine protective efficacy, 56.8%; CI 23% to 76%), and outbreak-associated influenza-like illnesses (6 of 162 vaccine recipients compared with 18 of 169 placebo recipients; vaccine protective efficacy, 65.0%; CI 17% to 86%).


CONCLUSIONS
Intranasal immunization with live attenuated influenza A virus vaccine provided additional protection against influenza A when added to parenteral trivalent inactivated influenza vaccine among elderly nursing home residents.
Treanor
J J
JJ
Infectious Disease Unit, University of Rochester, NY 14642.
Mattison
H R
HR
Dumyati
G
G
Yinnon
A
A
Erb
S
S
O'Brien
D
D
Dolin
R
R
Betts
R F
RF
D000281:Administration, Intranasal; D000368:Aged; D000369:Aged, 80 and over; D000914:Antibodies, Viral / Q000096:biosynthesis; D004196:Disease Outbreaks; D004311:Double-Blind Method; D005260:Female; D006707:Homes for the Aged; D006801:Humans; D009980:Influenza A virus / Q000276:immunology*; D007252:Influenza Vaccines / Q000008:administration & dosage* / Q000009:adverse effects / Q000276:immunology; D007251:Influenza, Human / Q000517:prevention & control*; D007273:Injections, Intramuscular; D008297:Male; D008875:Middle Aged; D009735:Nursing Homes; D014613:Vaccines, Attenuated / Q000008:administration & dosage; D015164:Vaccines, Inactivated / Q000008:administration & dosage
D000914:Antibodies, Viral; D007252:Influenza Vaccines; D014613:Vaccines, Attenuated; D015164:Vaccines, Inactivated