Reduced reaction frequencies with repeated inactivated or live-attenuated influenza vaccination

Impact of prior infection and repeated vaccination on post-vaccination antibody titers of the influenza A(H1N1)pdm09 strain in Taiwan schoolchildren: Implications for public health

BACKGROUND

The objective of this study was to evaluate the effects of prior-infection and repeated vaccination on post-vaccination antibody titers.

METHODS

A(H1N1)pdm09 strain was included in 2009 pandemic monovalent, 2010-2011, and 2011-2012 trivalent influenza vaccines (MIVpdm09, TIV10/11, TIV11/12) in Taiwan. During the 2011-2012 influenza season, we conducted a prospective sero-epidemiological cohort study among schoolchildren from grades 1 - 6 in the two elementary schools in Taipei with documented A(H1N1)pdm09 vaccination records since 2009. Serum samples were collected at pre-vaccination, 1-month, and 4-months post-vaccination (T1, T2, T3). Anti-A(H1N1)pdm09 hemagglutination inhibition titers (HI-Ab-titers) were examined. We also investigated the impact of four vaccination histories [(1) no previous vaccination (None), (2) vaccinated in 2009-2010 season (09v), (3) vaccinated in 2010-2011 season (10v), and (4) vaccinated consecutively in 2009-2010 and 2010-2011 seasons (09v + 10v)] and pre-vaccination HI-Ab levels on post-vaccination HI-Ab responses as well as adjusted vaccine effectiveness (aVE) against serologically-defined infection from T2 to T3.

RESULTS

TIV11/12 had zero serious adverse events reported. A(H1N1)pdm09 strain in TIV11/12 elicited seroprotective Ab-titers in 98% of children and showed promising protection (aVE: 70.3% [95% confidence interval (CI): 51.0-82.1%]). Previously unvaccinated but infected children had a 3.96 times higher T2 geometric mean titer (T2-GMT) of HI-Ab than those naïve to A(H1N1)pdm09 (GMT [95% CI]: 1039.7[585.3-1845.9] vs. 262.5[65.9-1045], p = 0.046). Previously vaccinated children with seroprotective T1-Ab-titers had a higher T2-GMT and a greater aVE than those with non-seroprotective T1-Ab-titers. Repeatedly vaccinated children had lower T2-GMT than those receiving primary doses of TIV11/12. However, after controlling prior infection and T1-Ab-titers, differences in T2-GMT among the four vaccination histories became insignificant (p = 0.16).

CONCLUSION

This study supports the implementation of annual mass-vaccination with A(H1N1)pdm09 in schoolchildren for three consecutive influenza seasons when vaccine and circulating strains were well matched, and found that prior infection and pre-vaccination HI-Ab levels positively impacted post-vaccination HI-Ab responses.

The immune response to 6-monthly versus annual standard dose inactivated trivalent influenza vaccination in older people: study protocol for a randomised clinical trial

Background

The seasonal influenza vaccine is less effective in older people and a single dose is unlikely to provide the year-round protection necessary for tropical climates which have year-round influenza virus activity. This study aims to assess the effect of a trivalent inactivated influenza vaccine (IIV3) booster at 180 days on haemagglutination-inhibition (HI) antibody titres for each of the influenza strains present in the administered vaccine in older people aged 65 years or above in Singapore.

Methods/design

This is a single-centre, randomised, observer-blind, active-comparator controlled, parallel-group, phase IV trial in 200 adults aged 65 years or older. Study participants will be assigned to one of two groups in a 1:1 ratio and followed for 1 year, with five scheduled visits. The control group will receive IIV3 at day 1, and an active comparator (Tetanus-diphtheria-pertussis vaccine) at day 180. Participants in the experimental group will receive IIV3 containing the same strains at day 1 and day 180. Endpoints are immunological, and include measures of HI titres, microneutralisation titres (MN) and cell-mediated immunity from first vaccination up to day 360.

Discussion

If superiority of 6-monthly influenza vaccination is demonstrated, this study could form the basis for a larger clinical trial with influenza infection as the primary endpoint.

Trial registration

ClinicalTrials.gov, ID: NCT02655874. Registered on 12 January 2016.

Electronic supplementary material

The online version of this article (doi:10.1186/s13063-017-1808-8) contains supplementary material, which is available to authorized users.

Evaluation of multivalent H2 influenza pandemic vaccines in mice

Subtype H2 Influenza A viruses were the cause of a severe pandemic in the winter of 1957. However, this subtype no longer circulates in humans and is no longer included in seasonal vaccines. As a result, individuals under 50years of age are immunologically naïve. H2 viruses persist in aquatic birds, which were a contributing source for the 1957 pandemic, and have also been isolated from swine. Reintroduction of the H2 via zoonotic transmission has been identified as a pandemic risk, so pre-pandemic planning should include preparation and testing of vaccine candidates against this subtype. We evaluated the immunogenicity of two inactivated, whole virus influenza vaccines (IVV) in mice: a monovalent IVV containing human pandemic virus A/Singapore/1/1957 (H2N2), and a multivalent IVV containing human A/Singapore/1/1957, avian A/Duck/HongKong/319/1978 (H2N2), and swine A/Swine/Missouri/2124514/2006 (H2N3) viruses. While both vaccines induced protective immunity compared to naïve animals, the multivalent formulation was advantageous over the monovalent in terms of level and breadth of serological responses, neutralization of infectious virus, and reduction of clinical disease and respiratory tissue replication in mice. Therefore, multivalent pandemic H2 vaccines containing diverse viruses from animal reservoirs, are a potential option to improve the immune responses in a pre-pandemic scenario where antigenic identity cannot be predicted.

Evaluating influenza vaccines: progress and perspectives

Severe influenza infections are responsible for 3–5 million cases worldwide and 250,000–500,000 deaths per year. Although vaccination is the primary and most effective means of inducing protection against influenza viruses, it also presents limitations. This review outlines the promising steps that have been taken toward the development of a broadly protective influenza virus vaccine through the use of new technologies. The future challenge is to develop a broadly protective vaccine that is able to induce long-term protection against antigenically variant influenza viruses, regardless of antigenic shift and drift, and thus to protect against seasonal and pandemic influenza viruses.

Options and obstacles for designing a universal influenza vaccine

Since the discovery of antibodies specific to a highly conserved stalk region of the influenza virus hemagglutinin (HA), eliciting such antibodies has been considered the key to developing a universal influenza vaccine that confers broad-spectrum protection against various influenza subtypes. To achieve this goal, a prime/boost immunization strategy has been heralded to redirect host immune responses from the variable globular head domain to the conserved stalk domain of HA. While this approach has been successful in eliciting cross-reactive antibodies against the HA stalk domain, protective efficacy remains relatively poor due to the low immunogenicity of the domain, and the cross-reactivity was only within the same group, rather than among different groups. Additionally, concerns are raised on the possibility of vaccine-associated enhancement of viral infection and whether multiple boost immunization protocols would be considered practical from a clinical standpoint. Live attenuated vaccine hitherto remains unexplored, but is expected to serve as an alternative approach, considering its superior cross-reactivity. This review summarizes recent advancements in the HA stalk-based universal influenza vaccines, discusses the pros and cons of these approaches with respect to the potentially beneficial and harmful effects of neutralizing and non-neutralizing antibodies, and suggests future guidelines towards the design of a truly protective universal influenza vaccine.

Role of viral RNA and lipid in the adverse events associated with the 2010 Southern Hemisphere trivalent influenza vaccine

In Australia, during the 2010 Southern Hemisphere (SH) influenza season, there was an unexpected increase in post-marketing adverse event reports of febrile seizures (FS) in children under 5 years of age shortly after vaccination with the CSL 2010 SH trivalent influenza vaccine (CSL 2010 SH TIV) compared to previous CSL TIVs and other licensed 2010 SH TIVs. In an accompanying study, we described the contribution to these adverse events of the 2010 SH influenza strains as expressed in the CSL 2010 SH TIV using in vitro cytokine/chemokine secretion from whole blood cells and induction of NF-κB activation in HEK293 reporter cells. The aim of the present study was to identify the root cause components that elicited the elevated cytokine/chemokine and NF-κB signature. Our studies demonstrated that the pyrogenic signal was associated with a heat-labile, viral-derived component(s) in the CSL 2010 SH TIV. Further, it was found that viral lipid-mediated delivery of short, fragmented viral RNA was the key trigger for the increased cytokine/chemokine secretion and NF-κB activation. It is likely that the FS reported in children <5 years were due to a combination of the new influenza strains included in the 2010 SH TIV and the CSL standard method of manufacture preserving strain-specific viral components of the new influenza strains (particularly B/Brisbane/60/2008 and to a lesser extent H1N1 A/California/07/2009). These combined to heighten immune activation of innate immune cells, which in a small proportion of children <5 years of age is associated with the occurrence of FS. The data also demonstrates that CSL TIVs formulated with increased levels of splitting agent (TDOC) for the B/Brisbane/60/2008 strain can attenuate the pro-inflammatory signals in vitro, identifying a potential path forward for generating a CSL TIV indicated for use in children <5 years.

Safety of a Trivalent Inactivated Influenza Vaccine in Health Care Workers in Kurdistan Province, Western Iran; A Longitudinal Follow-up Study

We studied the safety of a trivalent inactivated surface antigen (split virion, inactivated) influenza vaccine, Begrivac® (Novartis Company), widely used in health care workers in Kurdistan. A longitudinal follow-up study was performed in Sanandaj city, west of Iran, recruiting 936 people. A questionnaire was completed for each participant, and all symptoms or abnormal physical findings were recorded. In part 1 of the study, the post-vaccination complaints were headache (5.3%), fever (7.9%), weakness (9.6%), chills (10.1%), sweating (10.5%), arthralgia (20.2%), and malaise (21.5%). Swelling of the injection site was seen in 267 (30.3%) participants, and pruritus of the injection site was seen in 290 (32.9%) participants. Redness and induration were also reported in 42.5% of the participants. Local reactions were mainly mild and lasted for 1-2 days. No systemic reactions were reported in the second part of the study. None of the participants experienced any inconvenience. We concluded that local adverse reactions after the trivalent inactivated split influenza vaccine, Begrivac®, in health care workers were far more common than expected. Continuous surveillance is needed to assess the potential risks and benefits of newly produced influenza vaccines.

A postmarketing evaluation of the safety of Ann Arbor strain live attenuated influenza vaccine in adults 18-49 years of age

BACKGROUND

The Ann Arbor strain-live attenuated influenza vaccine (LAIV) was licensed in 2003 for use in the United States for individuals aged 5-49 years of age. As part of a postmarketing commitment to safety, LAIV was studied in adults 18-49 years participating in the Kaiser Permanente Health Plan over 5 influenza seasons.

METHODS

Individuals received LAIV as part of routine care from October 2003 through March 2008. Using Kaiser Permanente databases, rates of medically attended events (MAEs) and serious adverse events (SAEs) in LAIV recipients were compared with rates in multiple non-randomized control groups which included a self-control group, matched unvaccinated controls, and matched controls vaccinated with inactivated influenza vaccine (TIV).

RESULTS

A total of 21,340, 18,316, and 21,340 subjects received LAIV, TIV and no vaccine, respectively. More than 5500 MAE incidence rate comparisons were performed, and of these, 257 (5%) yielded statistically significant differences with 72 and 185 occurring at a higher and lower rate after LAIV compared with control groups, respectively. The pattern of MAE rate differences did not suggest any safety signal associated with LAIV. There were 47 SAEs noted, and no individual SAE occurred at a significantly higher or lower rate in LAIV recipients relative to control groups in any comparison. Only 2 SAEs (migraine/sinusitis and Bell's palsy) were considered possibly or probably related to LAIV.

CONCLUSION

The results of this post-licensure evaluation of LAIV safety in individuals 18-49 years of age are consistent with pre- and post-approval clinical studies as well as reports to the U.S. Vaccine Adverse Events Reporting System, all of which demonstrated no significant adverse outcomes among eligible individuals following receipt of LAIV.

Lactobacillus GG as an immune adjuvant for live-attenuated influenza vaccine in healthy adults: a randomized double-blind placebo-controlled trial

Background/Objectives

Live attenuated influenza vaccine (LAIV) protects against influenza by mucosal activation of the immune system. Studies in animals and adults have demonstrated that probiotics improve the immune response to mucosally delivered vaccines. We hypothesized that Lactobacillus GG (LGG) would act as an immune adjuvant to increase rates of seroconversion after LAIV administration.

Subjects/Methods

We conducted a randomized double-blind placebo-controlled pilot study to determine if LGG improved rates of seroconversion after administration of LAIV. We studied 42 healthy adults during the 2007–8 influenza season. All subjects received LAIV and then were randomized to LGG or placebo twice daily for 28 days. HAI titers were assessed at baseline, day 28, and day 56 to determine rates of seroconversion. Subjects were assessed for adverse events throughout the study period.

Results

39 subjects completed the per protocol analysis. Both LGG and LAIV were well tolerated. Protection rates against the vaccine H1N1 and B strains was similar suboptimal in subjects receiving LGG and placebo. For the H3N2 strain, 84% receiving LGG vs. 55% receiving placebo had a protective titer 28 days after vaccination (odds of having a protective titer was 1.84 95% CI 1.04–3.22, P=0.048).

Conclusion

Lactobacillus GG is potential as an important adjuvant to improve influenza vaccine immunogenicity. Future studies of probiotics as immune adjuvants may need to consider specifically examining vaccine naïve or seronegative subjects, target mucosal immune responses, or focus on groups known to have poor response to influenza vaccines.