Mouse response to influenza immunosomes

Immunosome preparations consisting of surface glycoproteins, extracted from five influenza virus strains and anchored onto preformed liposomes, were tested in mice. Serum antibody responses were essentially similar to those elicited by whole virus vaccines and higher than responses induced by subunit preparations. Antibody titres were assessed by haemagglutination-inhibition technique. Survival of mice immunized with 6 μg haemagglutinin of attenuated, inactivated, subunit or immunosome A/Aichi/2/68 vaccines and later challenged with variants of the same subtype was also assessed. All vaccine preparations induced similar percentage survival when mice were challenged with variants prevalent from 1968 to 1977. However, the attenuated vaccine induced a significant higher protection level against the 1979 variant.     

Responses to one or two doses of a deoxycholate subunit influenza vaccine in a primed population

A trial with a trivalent influenza subunit vaccine prepared with sodium deoxycholate was carried out in 88 volunteers between May and November 1981. Each haemagglutinin antigen was present at 7 μg per dose. Fourfold or greater haemagglutination inhibition antibody (HI) responses to the H1N1 virus A/Brazil/11/78 occurred in 70% of the volunteers following a single dose. For the H3N2 virus A/Bangkok/1/79 and B/Singapore/222/79 these figures were 52 and 11%, respectively. No increase in the antibody titre was noted to any of the antigens following a second vaccination dose. Antibody levels remained relatively constant six months after vaccination. A response to B/Singapore/222/79, comparable with the HI response for the influenza A antigens, was noted when serum titres were estimated by a plaque reduction procedure. No neuraminidase inhibition antibody could be detected in response to either A/Brazil/11/78 or A/Bangkok/1/79. No reactions specifically attributable to the vaccine occurred after either injection. A lower HI response to A/Brazil/11/78 was noted in volunteers 52 years of age and older, who also showed less evidence of earlier priming to this virus. Levels of nasal wash neutralizing antibodies to A/Brazil/11/78 were proportional to those detected in sera by HI tests, but were present in smaller amounts.     

两种流行性感冒病毒裂解疫苗安全性与免疫原性研究

目的：评价国产流行性感冒裂解疫苗的安全性和免疫原性。方法：按整群随机抽样原则,以进口同类疫苗作为对照开展现场临床试验;比较两种疫苗免后不良反应率、抗体阳转率、保护率及几何平均滴度（GMT）。结果：试验组及对照组接种后全身不良反应率分别为2．7％和3．6％（P〉0．05）,局部不良反应率分别为7．2％和9．6％（P〉O．05）;试验疫苗流感病毒HINI、H3N2及B（亚）型的HI抗体总阳转率分别为81．6％,92．4％和78．0％;对照疫苗流感病毒HIN1、H3N2及B（亚）型的HI抗体总阳转率分别为87．1％,88．3％0和80．8％,三（亚）型流感抗体总阳转率差异无统计学意义;三（亚）型流感HI抗体达到保护水平的保护率的比较中,只有婴幼儿试验组和对照组的免后B型HI抗体滴度≥1：40,差异有统计学意义,试验组大于对照组,其余3组差异无统计学意义;三（亚）型流感抗体免后GMT的差异亦无统计学意义。结论：国产流感裂解疫苗全身和局部不良反应与进口同类疫苗无差异,免后抗体阳转率较高,抗体滴度上升幅度较大,具有良好的安全性和免疫原性。     

流行性感冒病毒裂解疫苗质量控制与稳定性研究

[目的 ]　研制安全有效的流行性感冒病毒裂解疫苗。　 [方法 ]　将A1,A3和B三株流感病毒分别接种鸡胚 ,收取尿囊液 ,经乙醚裂解病毒 ,制成疫苗。　 [结果 ]　该疫苗主要技术指标均符合WHO规程要求 ,并具有良好的免疫效果 ,同时稳定性试验取得令人满意的结果。　 [结论 ]　该疫苗是安全有效的     

The hemagglutination inhibition antibody responses to an inactivated influenza vaccine among healthy adults: with special reference to the prevaccination antibody and its interaction with age

The immunogenicity of the trivalent split-virus influenza vaccine was investigated among 70 healthy adults (mean age: 48.5, range: 36–68). The vaccine antigens were: A/Yamagata/32/89 (H1N1); A/Beijing/352/89 (H3N2); and B/Bangkok/163/90. Regarding the entire sample, the vaccine induced a tenfold or more rise on the average in the hemagglutination inhibition (HAI) antibody to each antigen. The response rates (greater than or equal to a fourfold rise) were about 90% or more among those with a prevaccination titer ≤1:64 (equivalent to ≤1:16 on the Western scale: in Japan, the HAI titers are expressed by the final, and not the initial, dilution of the serum; from hereon our findings will be expressed using the Japanese scale), whereas they were 0–50% at ≥1:128. Thus, the prevaccination titer was negatively associated with antibody induction. The achievement rates (postvaccination titer ≥1:128) among those with a prevaccination titer <1:16 remained at 48–68%. Regarding the analysis of variance, a significant effect on antibody induction was indicated for the prevaccination titer (P≤0.002), but not for age (P≥0.425). The interaction between the prevaccination titer and age was significant for A/Yamagata (P=0.030), while it was also suggestive for A/Beijing (P=0.054): as age increased, those with no preexisting antibody (<1:16) showed greater titer rises, in contrast to the smaller rises among those with a titer ≥1:16. Based on the attack survey conducted separately, the vaccine efficacy on influenza-like illnesses with fever ≥37°C and ≥37.5°C was calculated to be 16% (95% confidence interval: −66% to 57%) and 37% (−55% to 74%), respectively.     

Neutralizing antibody but not hemagglutination antibody provides accurate evaluation for protective immune response to H5N1 avian influenza virus in vaccinated rabbits

In order to develop an animal model and an assay method to evaluate protective immune response to H5N1 avian influenza vaccination, H5N1 avian influenza vaccine was prepared. New Zealand rabbits were assigned to receive two doses of vaccine with different hemagglutinin (HA) dosage. The sera from vaccinated rabbits was evaluated to determine antibody titer and specificity using different tested methods including hemagglutination inhibition assay (HI), neutralizing assay (NT), cross-HI assay, cross-single immunodiffusion assay and cross-neutralization assay. The titer of HI antibody from rabbits immunized with different doses of HA were no less than 1:40 among groups 14 days after the first immunization. Whereas the NT antibody titer was less than 1:10 among groups 14 days after the first immunization. NT antibodies can be detected 14 days after the second immunization in rabbits immunized at HA doses higher than 6 μg, and the NT antibody titers were equal to or higher than 1:40. A good concentration-dependent NT antibody response can be detected in the vaccinated rabbits 14 days after the second immunization, and in contrast, no concentration-dependent relationship can be seen for HA antibody. The cross-HI test showed sera from vaccinated rabbits could cross react with influenza A H5N1 virus with the titers higher than 1:40. No cross reaction among different types (influenza A/H1N1 virus, influenza A/H3N2 virus, influenza B virus and influenza A/H5N1 virus) can be detected in the sera using the single immunodiffusion assay and using NT antibody test. This showed NT antibody test was demonstrated as a more accurate assay method for evaluating vaccination and quality of the vaccine than HI antibody test.     

Antibody responses and protection in mice immunized orally against influenza virus

Antibody responses and protection were studied in BALB/c mice immunized orally with formalin-inactivated influenza viruses (A/PR/8/34) combined with cholera toxin B subunit as adjuvant. Influenza virus-specific IgA as well as IgG antibody responses were induced in the mice, depending on the oral dosage frequency. The oral immunization by multiple doses resulted in reduction of viral replication in the nose and prevention of development of infection in the lung after intranasal (i.n.) challenge. The protective effect in the nose was thought to be related to the nasal IgA antibody response. The oral immunization was, however, less efficient for induction of the IgA antibody response and protection in the nose, compared with an i.n. immunization. The oral immunization following subcutaneous priming led to the complete protection in the nose, accompanied by a prompt local IgA antibody response.     

Immunopotentiation of humoral and cellular responses to inactivated influenza vaccines by two different adjuvants with potential for human use

Two quite different adjuvants, currently under development for use in humans, have been examined for their effects on the magnitude and type of immunity elicited in response to inactivated influenza vaccine. Immunostimulating complexes (ISCOM™ adjuvant) contain the saponin ISCOPREP™ 703, and SPT is an oil-in-water emulsion of squalane, non-ionic block copolymer (L121) and Tween 80. Influenza virus vaccines formulated in either adjuvant were far superior to the non-adjuvanted aqueous vaccine in eliciting antibody and T-cell responses in mice, particularly at lower doses of antigen. In addition, the vaccines containing adjuvant were superior in eliciting protective immunity. One of the shortcomings of the unadjuvanted inactivated influenza vaccine was its inability to elicit a primary proliferative T-cell response. However, after one dose of either adjuvaned vaccine, strong proliferative responses were achieved. We also show that subcutaneous vaccination with inactivated vaccines is capable of modulating the isotype profile of antibody secreting cells generated in the lungs of mice in response to intranasal challenge with live virus. In this system, the isotype of antibody elicited after challenge of mice that had received ISCOM vaccine more closely mimicked that of animals vaccinated with live virus.     

进口加拿大流行性感冒裂解疫苗临床安全性与免疫原性评价

目的 评价加拿大Shire公司生产的流行性感冒(流感)裂解疫苗的安全性和免疫原性。方法 按整群随机抽样原则，以进口同类疫苗作为对照开展现场临床试验；比较两种流感疫苗免疫后临床反应率、抗体阳转率、保护率及几何平均滴度(GMT)。结果 试验组发热反应率(3．69％)及局部反应率(1．75％)与对照组相比较，两组间差异无统计学意义。试验组、对照组免疫后H1N1、H3N2、B型抗体阳转率分别为96．8％、95．8％、52．3％和92．3％、90．2％、62．3％；结果显示两种流感疫苗间阳转率差异有统计学意义。试验组和对照组的H1N1、H3N2及B(亚)型抗体GMT平均增长倍数分别为22．4、16．8、8．2倍和21．2、12．5、7．4倍；试验组免疫后H1N1、H3N2、B型抗体保护率(99％、99％、53．9％)与对照组免疫后三型保护率(96．2％、98．4％、62．3％)差异无统计学意义。结论 加拿大Shire公司生产的流感裂解疫苗发热反应和局部反应与进口同类疫苗无差异，临床安全性良好；免疫后抗体阳转率较高，抗体滴度上升幅度较大，具有良好的免疫原性。     

Cost-effectiveness analysis of quadrivalent seasonal influenza vaccines in Beijing: A modeling analysis

BackgroundSince 2007, Beijing has offered a free trivalent influenza vaccine (TIV) for residents aged ≥ 60 years and school students. The quadrivalent influenza vaccine (QIV) was administered to school children in 2018 and will be administered to elderly adults in the future. In addition, health care workers (HCWs) who are involved in the prevention and control of COVID-19 were included in the program in 2020. This study aimed to analyze the cost-effectiveness of a comprehensive list of combined strategies of TIV and QIV for school children, elderly adults, and HCWs to identify the most cost-effective strategy.MethodsA decision tree was developed to compare 1-year outcomes of TIV vs. QIV in three risk groups: school children, elderly adults, and HCWs. The outcome was incremental cost per quality-adjusted life-year (QALY). Probabilistic sensitivity analyses and scenario analyses were developed to assess the robustness of the results.ResultsFrom the perspective of society, this study found that the introduction of QIVs can be cost-effective for any and all targeted groups with a willingness-to-pay threshold of 3-fold GDP per capita. Among all programs, program H (all school children, elderly adults, and HCWs received the QIV) showed a 79% probability of being cost-effective with an incremental cost-effectiveness ratio (ICER) of 13,580 (95% CI: 13,294, 13,867) US$/QALY and was the preferred option in the base case scenario.ConclusionThe introduction of QIVs to school children, elderly adults, or HCWs is likely to be cost-effective, either separately or collectively. The introduction of QIV to school children, elderly adults, and health care workers simultaneously showed the highest probability of being cost-effective and was the preferred option.     

国产流感裂解疫苗接种人体后安全性和免疫原性评价

目的:评价变更后流感毒株生产的国产流感裂解疫苗安全性和免疫原性。方法:对宁波市宁海县559例分组接种流感裂解疫苗者进行临床指标(局部反应、全身反应)的监测,并抽取其中213例,用流感病毒HI抗体测定法对接种者免疫前后的抗体滴度进行测定,比较免疫前后抗体阳转率及几何平均滴度(GMT)。结果:观察对象接种疫苗后发热反应发生率为1.22%,全身其他反应发生率为1.22%,局部反应发生率为1.07%,且以轻度反应为主。H1N1型、H3N2型、B型免后抗体阳转率分别为84.04%、85.45%、83.57%;不同年龄组免后抗体滴度的增长倍数,H1N1型在5.50～16.00倍之间,H3N2型在13.16～39.33倍之间,B型在7.28～24.85倍之间,各年龄组各抗体型别免疫前后GMT差别均有统计学意义。结论:国产流感裂解疫苗具有良好的安全性和免疫原性。     

Safety and immunogenicity of three seasonal inactivated influenza vaccines among pregnant women and antibody persistence in their infants

ObjectiveInactivated influenza virus vaccines (IIVs) are recommended for all pregnant women in the United States. We conducted a prospective, randomized, double blind study of three licensed seasonal trivalent IIVs (IIV3s) to assess their safety and immunogenicity in pregnant women and determine the level and persistence of passively transferred maternal antibody in infants.Study design139 pregnant women ages 18–39 years and 14–33 weeks’ gestation, and 44 non-pregnant women, were randomized 1:1:1 to receive a single intramuscular dose of one of three licensed IIV3s (Agriflu®, Fluzone®, or Fluarix®) prior to the 2010–2011 influenza season. Reactogenicity, adverse events (AEs) and pregnancy outcomes were documented. Serum samples for hemagglutination inhibition (HAI) and neutralization antibody assays were collected prior to and 28 and 180 days after immunization. Maternal sera and cord blood were collected at the time of delivery and sera were obtained from 44 infants at 6 weeks of age.ResultsPregnant and non-pregnant women experienced similar frequency of injection site (92% and 86%, respectively) and systemic (95% and 87%, respectively) reactions, the majority of which were mild. There were no vaccine-associated maternal or infant serious AEs. Antibody responses to the three vaccine antigens were not different between pregnant and non-pregnant women. The ratios of cord blood (infant) to maternal HAI antibody titers at delivery ranged between 1.1 and 1.7 for each of the vaccine antigens. Influenza antibody concentrations in infants were 70–40% of the birth titer by 6 weeks of age.ConclusionsThe three IIV3s were well tolerated in pregnant women. Antibody responses were comparable in pregnant and non-pregnant women, and after second or third trimester vaccination. Transplacental transfer of maternal antibodies to the infant was efficient. However, antibody titers decline rapidly in the first 6 weeks of life.     

Protective immunity against influenza virus challenge by norovirus P particle-M2e and HA2-AtCYN vaccines in chickens

Development of a broadly reactive influenza vaccine that can provide protection against emerging type A influenza viruses is a big challenge. We previously demonstrated that a vaccine displaying the extracellular domain of the matrix protein 2 (M2e) on the surface loops of norovirus P-particle (M2eP) can partially protect chickens against several subtypes of avian influenza viruses. In the current study, a chimeric vaccine containing a conserved peptide from the subunit 2 of hemagglutinin (HA) glycoprotein (HA2) and Arabidopsis thaliana cyanase protein (AtCYN) (HA2-AtCYN vaccine) was evaluated in 2-weeks-old chickens. Depending on the route of administration, the HA2-AtCYN vaccine was shown to induce various levels of HA2-specific IgA in tears as well as serum IgG, which were associated with partial protection of chickens against tracheal shedding of a low pathogenicity H5N2 challenge virus. Furthermore, intranasal administration with a combination of HA2-AtCYN and M2eP vaccines resulted in enhanced protection compared to each vaccine alone. Simultaneous intranasal administration of the vaccines did not interfere with secretory IgA induction by each vaccine. Additionally, significantly higher M2eP-specific proliferative responses were observed in peripheral blood mononuclear cells of all M2eP-vaccinated groups when compared with the mock-vaccinated group. Although tripling the number of M2e copies did not enhance the protective efficacy of the chimeric vaccine, it significantly reduced immunodominance of P-particle epitopes without affecting the robustness of M2e-specific immune responses. Taken together, our data suggests that mucosal immunization of chickens with combinations of mechanistically different cross-subtype-conserved vaccines has the potential to enhance the protective efficacy against influenza virus challenge.     

Inactivated influenza virions are a flexible vaccine platform for eliciting protective antibody responses against neuraminidase

Most seasonal influenza vaccines are produced using hemagglutinin (HA) surface antigens from inactivated virions. However, virions are thought to be a suboptimal source for the less abundant neuraminidase (NA) surface antigen, which is also protective against severe disease. Here, we demonstrate that inactivated influenza virions are compatible with two modern approaches for improving protective antibody responses against NA. Using a DBA/2J mouse model, we show that the strong infection-induced NA inhibitory (NAI) antibody responses are only achieved by high dose immunizations of inactivated virions, likely due to the low viral NA content. Based on this observation, we first produced virions with higher NA content by using reverse genetics to exchange the viral internal gene segments. Single immunizations with these inactivated virions showed enhanced NAI antibody responses and improved NA-based protection from a lethal viral challenge while also allowing for the development of natural immunity to the heterotypic challenge virus HA. Second, we combined inactivated virions with recombinant NA protein antigens. These combination vaccines increased NA-based protection following viral challenge and elicited stronger antibody responses against NA than either component alone, especially when the NAs possessed similar antigenicity. Together, these results indicate that inactivated virions are a flexible platform that can be easily combined with protein-based vaccines to improve protective antibody responses against influenza antigens.     

禽流感病毒研究进展及抗H7N9型病毒疫苗与抗体研究

禽流感病毒（avian influenza virus,AIV）是一种可引起急性呼吸道传染病的人畜共患病毒。自2013年我国出现了全球首例人感染H7N9型AIV病例以来,人们对该病毒产生了担忧与恐慌。AIV在全球广泛传播,人感染不同型别AIV事件也持续发生,造成了巨大的经济损失。目前尚无针对该病的特异性治疗措施与药物,...     

Immunologic evaluation of 10 different adjuvants for use in vaccines for chickens against highly pathogenic avian influenza virus

Avian influenza viruses (AIV) are a threat to poultry production worldwide. Vaccination is utilized as a component of control programs for both high pathogenicity (HP) and low pathogenicity (LP) AIV. Over 95% of all AIV vaccine used in poultry are inactivated, adjuvanted products. To identify the best formulations for chickens, vaccines were prepared with beta-propiolactone (BPL) inactivated A/British Columbia/314514-1/2004 H7N3 LP AIV using ten commercially available or experimental adjuvants. Each vaccine formulation was evaluated for immunogenicity in chickens. Challenge studies with an antigenically homologous strain of HPAIV were conducted to compare protection against mortality and measure reductions in virus levels in oral swabs. The four best adjuvants from the studies with BPL inactivated antigen were selected and tested identically, but with vaccines prepared from formalin inactivated virus. Mineral and vegetable oil based adjuvants generally induced the highest antibody titers with 100% seroconversion by 3 weeks post vaccination. Chitosan induced positive antibody titers in 100% of the chickens, but the titers were significantly lower than those of most of the oil based adjuvants. Antibody levels from calcium phosphate and alginate adjuvanted groups were similar to those of non-adjuvanted virus. All groups that received adjuvanted vaccines induced similar levels of protection against mortality (0–20%) except the groups vaccinated with calcium phosphate adjuvanted vaccines, where mortality was similar (70%) to groups that received non-adjuvanted inactivated virus or no vaccine (60–100% mortality). Virus shedding in oral swabs was variable among the treatment groups. Formalin inactivated vaccine induced similar antibody titers and protection against challenge compared to BPL inactivated vaccine groups. These studies support the use of oil adjuvanted vaccines for use in the poultry industry for control for AIV.     

Use of a zwitterionic detergent for the preparation of an influenza virus vaccine: 2. Immunogenicity of Empigen-treated virus in animals

The immunogenicity of zwitterionic detergent-disrupted influenza virus vaccine preparations, intact virus vaccine and vaccine preparations obtained by treatment of the intact virus with Triton-X 100 or cetyl trimethyl ammonium bromide (CTAB) was studied in hamsters and mice. In all experiments the intact, inactivated virus vaccine induced greater serum haemagglutination-inhibiting (HI) and neuraminidase-inhibiting (NI) antibody titres than the detergent-disrupted preparations. The serum HI antibody responses induced in hamsters and mice by Empigen-, Triton-, or CTAB-disrupted vaccines were similar, although more highly purified Empigen-disrupted preparations elicited marginally lower immune responses. In both animal species, all vaccine preparations afforded a similar degree of protection against homologous virus challenge.     

Comparison of the immunogenicity and safety of quadrivalent and tetravalent influenza vaccines in children and adolescents

BackgroundChildren and adolescents are susceptible to influenza. Vaccination is the most important strategy for preventing influenza, yet there are few studies on the immunogenicity and safety of quadrivalent inactivated influenza vaccine (QIV) containing two A strains (H1N1 and H3N2) and two B lineages (Victoria and Yamagata). Therefore, to further clarify the immunogenicity and safety of QIV in children and adolescents, a meta-analysis was performed to provide a reference for the development of influenza prevention strategies.MethodsPubMed, EMBASE and Cochrane Library were searched for articles published as of February 12, 2019. Random clinical trials comparing the immunogenicity and safety of QIV and TIV among children and adolescents were selected. The main outcomes were comparisons of immunogenicity (seroprotection rate [SPR] and seroconversion rate [SCR] and adverse events using risk ratios (RRs). The meta-analysis was performed using random-effects models.ResultsAmong the 6 months up to 3 years group, QIV showed a higher SPR for B lineages than for TIV-B/Yamagata, with pooled RRs of 3.07 (95% CI: 2.58–3.66) and 1.06 (95% CI: 1.01–1.11), respectively. For the 3 years through 18 years, QIV had a higher SCR and SPR for the Yamagata lineage than for TIV-B/Victoria, with pooled RRs of 2.30 (95% CI: 1.83–2.88) and 1.16 (95% CI: 1.03–1.30), respectively. Compared to TIV-B/Yamagata, a higher SCR and SPR for the Victoria lineage was found for QIV, with RRs of 3.09 (95% CI: 1.99–4.78) and 1.72 (95% CI: 1.22–2.41), respectively. Regarding adverse events, only pain was more frequently reported for QIV than TIV ; the RR was 1.09 (95% CI: 1.02–1.17).ConclusionsThe immunogenicity of QIV for common ingredients was similar to that of TIV, but the former exhibited significantly higher immunogenicity for the unique lineage. QIV also had the same reliable safety as TIV.     

Expression of enhancing-activity-free neutralizing antibody against dengue type 1 virus in plasmid-inoculated mice

BackgroundMost candidate dengue vaccines currently under development induce neutralizing antibodies, which are considered important for immunoprotection. However, the concomitant induction of infection-enhancing antibodies is an unavoidable concern. In contrast, a neutralizing antibody developed for passive immunotherapy has been engineered to eliminate its enhancing activity. Therefore, a strategy for the long-term expression of enhancing-activity-free neutralizing antibodies may resolve this concern.MethodsA mouse monoclonal antibody, 7F4, of the IgG3 subclass and with no detectable enhancing activity, was selected as the model neutralizing antibody to evaluate the potential of this strategy. Equal amounts of commercial vector (pFUSE)-based plasmids containing 7F4 heavy (H)- or light (L)-chain variable region genes were mixed and used for the cotransfection of 293T cells and co-delivery into ICR and BALB/c mice. The recombinant plasmids were designed to express IgG2b or IgG3 subclass antibodies (p7F4G2b or p7F4G3, respectively).Results293T cells transfected with 2 μg of p7F4G2b or p7F4G3 produced approximately 15,000 or 800 ng/ml IgG in the culture fluids, respectively. The dose is expressed as the total amount of H- and L-chain plasmids. Neutralizing antibody was detected dose-dependently in ICR mice inoculated with 50–200 μg of p7F4G2b. A 1:2 dilution of sera from ICR and BALB/c mice inoculated with 100 μg of p7F4G3 showed average plaque reduction levels of >70% on day 3 and >90% on days 5–9. BALB/c mice maintained detectable neutralizing antibody for at least 3 months. The neutralizing antibody expressed by p7F4G3 in mice showed no enhancing activity.DiscussionAlthough the expression of neutralizing antibodies from immunoglobulin genes is a type of passive immunization, its durability can be utilized as a dengue vaccine strategy. This “proof-of-concept” study using a mouse model demonstrates that the enhancing-activity-free characteristic of this strategy augurs well for dengue vaccine development, although further improvement is required.     

Safety and immunogenicity of seasonal trivalent inactivated influenza vaccines in pregnant women

BackgroundIn the United States, seasonal inactivated influenza vaccine (IIV) is recommended for pregnant women; however, in early 2009, immunization rates were low, partly due to limited prospective data and concerns about vaccine safety.ObjectiveWe conducted a randomized study of two licensed seasonal trivalent IIVs (IIV3) to assess their safety and immunogenicity in pregnant women.Study DesignIn this prospective, randomized clinical study, 100 pregnant women, 18–39 years of age and ≥14 weeks gestation received a single intramuscular dose of 2008–2009 Fluzone® or Fluarix®. Injection site and systemic reactions were recorded for 7 days after vaccination and serious adverse events (SAEs) and pregnancy outcomes were documented. Serum samples collected before and 28 days after vaccination were tested for hemagglutination inhibition (HAI) antibody levels.ResultsThe majority of the injection site and systemic reactions were mild and self-limited after both vaccines. No fever ≥100 °F was reported. There were no vaccine-associated SAEs. Immune responses to influenza vaccine antigens were similar for the two study vaccines, with robust HAI responses against influenza A strains, and relatively lower responses for influenza B strains.ConclusionSeasonal inactivated influenza vaccines were well tolerated and immunogenic in pregnant women.

• ClinicalTrials.gov identifier NCT00905125.

Synopsis: In this prospective clinical trial, we demonstrated that immunization with seasonal trivalent, inactivated influenza vaccine in the second and third trimester of pregnancy is immunogenic and safe.