Add two previous reports of the low immunogenicity of H7N9 HA, one from NovaVax, stating that their unadjuvanted vaccine is only 6-16% effective and Novartis – showing only 6% seroconversion for their unadjuvanted HA vaccine) to this report – and you have a slam dunk – three independent verifications that our tools accurately predict vaccine (and immunogen) efficacy. For reference, most unadjuvanted HA-based vaccines produce at least 75% seroconversion. H7N9 is a true outlier. . .  Can we say we told you so?

Details on the latest publication that concurs with EpiVax that H7N9 is a ‘Stealth’ virus are below, from ProMed:

Published Date: 2014-01-04 17:02:39
Subject: PRO/AH/EDR> Avian influenza, human (03): China, H7N9 weak antibody response
Archive Number: 20140104.2151752

A ProMED-mail post
ProMED-mail is a program of the
International Society for Infectious Diseases

Date: Thu 2 Jan 2014
Source: CIDRAP (Center for Infectious Disease Research & Policy) News [edited]

Serum study finds weak antibody response to H7N9
Researchers who examined the blood of patients infected with novel H7N9 influenza found a weak antibody response to the strain, which might shed light on disease pathogenesis and suggests that multiple doses of vaccine may be needed to provide protection. The study, by a team from China, appeared yesterday [1 Jan 2014] in an early online edition of Emerging Infectious Diseases.

The authors focused on 48 samples collected from 21 patients sickened in the ongoing H7N9 outbreak, 19 from Shanghai and 2 from Beijing; paired samples were obtained in 15 of the patients. Of the samples, 21 were from the acute phase, 18 were convalescent, and 9 were obtained between 102 and 125 days after symptom onset. For controls, the team included 100 blood samples collected in 2008 from healthy donors in Beijing and 77 samples collected in May and June 2013 from poultry workers in Shanghai.

Protective antibody response to H7N9 was relatively weak, with neutralizing antibody response lower than the response to the 2009 H1N1 and H5N1 viruses. Also, serum IgG avidity for H7 was lower than that for H1 and H3. In addition, the group found a correlation between IgG levels against H3 in acute-phase serum and IgG levels against H7 in convalescent serum.

The findings raise questions about the role of humoral responses in H7N9 disease severity and duration, the team wrote. They also said scientists should examine the cross-reactivity between H7 and H3 and determine whether any boost response could occur from H3N2 infection.

Communicated by:
ProMED-mail Rapporteur Mary Marshall

[The publication referred to above is, Guo L, Zhang X, Ren L, et al: Human Antibody Responses to Avian Influenza A(H7N9) Virus, 2013
Emerg Infect Dis [Internet] 2014; 20(2);

The Abstract reads:
“Understanding host antibody response is crucial for predicting disease severity and for vaccine development. We investigated antibody responses against influenza A(H7N9) virus in 48 serum samples from 21 patients, including paired samples from 15 patients. IgG against subtype H7 and neutralizing antibodies (NAbs) were not detected in acute-phase samples, but ELISA geometric mean titers increased in convalescent-phase samples; NAb titers were 20-80 (geometric mean titer 40). Avidity to IgG against subtype H7 was significantly lower than that against H1 and H3. IgG against H3 was boosted after infection with influenza A(H7N9) virus, and its level in acute-phase samples correlated with that against H7 in convalescent-phase samples. A correlation was also found between hemagglutinin inhibition and NAb titers and between hemagglutinin inhibition and IgG titers against H7.”

Because of the relatively weak protective antibody response to avian influenza A(H7N9) infection, one of the authors’ conclusions is that multiple vaccinations might be needed to achieve protective immunity in humans. – Mod.CP

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