Intention and hesitancy to receive a booster dose of COVID-19 vaccine among pregnant women using a health belief model: A cross-sectional study

Objective:To examine the pattern of COVID-19 infection and vaccination,and to explore pregnant women’s willingness and reluctance to accept a booster dose of the COVID-19 vaccine.Methods:This was a cross-sectional,descriptive study with a convenient sample size using a structured questionnaire among pregnant women attending the gynecology and obstetrics department at Acıbadem Mehmet Ali Aydinlar Hospital,Istanbul,Türkiye.The Health Belief Model scale was used to assess the intention and reluctance to accept a booster dose of the COVID-19 vaccine.Results:A total of 145 participants,with a mean age of(33.5±4.8)years,and a gestational age of(30.9±7.3)weeks,were enrolled in this study.88.8%Received full doses of the Pfizer-BioNTech vaccination.47.8%Participants suffered from vaccine adverse effects.Health Belief Model demonstrated a significant finding of perceived susceptibility(P<0.001),perceived severity of COVID-19 complications(P<0.001),and perceived benefits regarding a booster COVID-19 vaccination(P<0.001).Conclusions:Most pregnant women who received the COVID-19 immunization express a significant intention to receive a booster dose,regardless of the adverse effects experienced from the previous doses.However,a small percentage of the study sample express hesitancy about receiving the booster dose.

Effectiveness of COVID-19 Vaccine Doses in Children: Case of Lake Region Economic Bloc-Kenya

Introduction: Vaccination of children has experienced delays due to paucity of information regarding safety, effectiveness, immunogenicity, and reactogenicity. Age wise approval prioritized 12 - 17 years and later 5 - 11 years. Those below 5 years possess na?ve immunity and not considered. In Lake Region Economic Bloc children aged 12 - 17 variably received 1, 2, and 3 doses of vaccine. This analysis looks into effectiveness of the doses administered. Method: Data providers from 84 LREB facilities submitted patients’ vaccination data to Power BI supported dashboard between June 24, 2021 and July 30, 2022. Data of 12 - 17 years old was mined, analyzed and visualized. Sample sizes considered for analysis were 0 dose, n = 8132;1 dose, n = 271;2 doses, n = 402, and 3 doses, n = 90. Data used in the analysis was facility operational and not from experimental design. Relative risk analysis of children who received 0, 1, 2, and 3 doses was done using Odds Ratio run on R software. Results: The relative risk of infection to a child with one dose against unvaccinated counterpart is 0.92 (95% CI, 0.61 - 1.43). Likewise the relative risk of infection to a child aged 12 - 17 years with 2 doses against another who received no dose is 0.87 (95% CI, 0.63 - 1.24). A child with 3 doses is 46% (95% CI, 27% - 84%) less likely to get infected compared to another not vaccinated. Also, the relative risk between having 2 doses and 1 dose for a child aged 12 - 17 years is 0.95 (95% CI, 0.55 - 1.6). For the same age group the relative risk of having 3 doses of vaccines against 1 dose is 51% (95% CI, 26% - 100%). In addition, a child who receives 3 doses of vaccine is 53% (95% CI, 28% - 100%) less likely to experience breakthrough infection compared to another with 2 doses. Whereas 1st dose offers (5%) marginal protection advantage over the 2nd dose, the 3r dose offers 49% and 47% more protection over 1st and 2nd doses, respectively, because of incremental reduced risk of infection gained from previous doses. During the period, 15 children at risk were admitted with COVID-19 infections in various regional hospitals, one had 3 doses but confounded with severe comorbidity. Conclusion: We found that 2nd dose had marginal protection over the 1st dose. However, the 3rd dose offers extensive protection compared to 1st and 2nd doses, and protects more against hospitalization. Children at risk should receive 3 doses of vaccines.

Religion and “Zero-Dose” Vaccination Status in Children Aged 12 to 23 Months in Benin and Togo: “Evidence of Demographic and Health Survey and Multiple Indicator Cluster Surveys”

Introduction: The relationship between religion and health has been a topic of interest in the past, and in recent years it has become increasingly visible in the social, behavioural, and health sciences. This work aims to study the influence of religion on the “zero-dose” vaccination status of children aged 12 - 23 months in Benin and Togo. Methods: This was a cross-sectional study which consisted in carrying out secondary analyzes using the databases of the most recent editions of the Demographic and Health Surveys in Benin and the Multiple Indicator Cluster Surveys (MICS) in Togo. We extracted data concerning the vaccination status (“1 = zero-dose”, “0 = vaccinated”) of the children, the religious affiliation of the head of the household or the mother and other variables related to the child, the mother, the household and the environment. By means of a logistic regression, the adjusted effect of the religious affiliation of the head of the household or of the mother on the vaccination status at “zero-dose” was determined. Results: A total of 2430 and 933 children were respectively included in the study on behalf of Benin and Togo. The prevalence of “zero-dose” vaccination status in children aged 12 - 23 months was 33.91% (95% CI = 31.67 - 36.23) in Benin and this prevalence was 26.88% (95% CI = 23.50 - 30.55) in Togo. In Benin, there is no evidence in favour of the influence of the religious affiliation of the mother on the “zero-dose” vaccination status of children. In Togo, children living in households whose head was Muslim (ORa = 3.44;95% CI = 1.29 - 9.13) were more likely to be “zero-dose” than those coming from households run by individuals with no religious beliefs. Conclusion: Further research is needed to understand the basis for the excess risk of “zero-dose” vaccination status in children that appears to be associated with the Muslim religion.

The Association of Hepatitis B Vaccine Supply Policy with Timing of Receipt of the First Dose of Hepatitis B Vaccination

An estimated 800,000 - 1.4 million persons in the US have chronic hepatitis B virus (HBV) infection. The risk for chronic infection is greatest among young children;approximately 90% of infants will remain chronically infected with HBV. Approximately 25% of those who become chronically infected during childhood die prematurely from cirrhosis or liver cancer. Hepatitis B vaccination is the most effective measure to prevent HBV infection and its consequences. In 2006, 29 US states had Hepatitis B Vaccine Supply (HBVS) policy which either supplies hepatitis B vaccine at no cost to all providers for all children or provides hepatitis B vaccine to delivery hospitals-only free of charge for all infants;other 21 US states and the District of Columbia did not have. 17,636 infants born in 2006 obtained from 2007-2009 National Immunization Survey (NIS) were analyzed with survival analysis procedures of Kaplan-Meier estimate and Cox proportional hazards model for complex sample survey to evaluate the association between state HBVS policy and the timing of infant age in days to receipt of hepatitis B vaccination. State HBVS policy is associated with infant age in days from birth to receipt of the first dose of hepatitis B vaccine (P < 0.01), and to completion of the 3-dose hepatitis B vaccine series (P < 0.01). Receipt of the first dose of hepatitis B vaccine occurred 31% earlier among infants residing in states with HBVS policy than among infants residing in states without (adjusted hazards ratio 1.31, 95%CI (1.23, 1.39)). Completion of the 3-dose hepatitis B vaccine series were 12% sooner among infants living in states with HBVS policy than among infants living in states without (adjusted hazards ratio 1.12, 95%CI (1.06, 1.18)). State HBVS policy may help overcome barriers to timely delivery of hepatitis B vaccines to infants.

Effect of 7 and 13-Valent Pneumococcal Conjugate Vaccines Different Number of Doses for Pneumonia Control in 2008 and 2010 Birth Cohort Children

The 7-valent pneumococcal conjugate vaccine (PCV) was introduced in Uruguay in March 2008. In April 2010, it was replaced by PCV13. Surveillance of both vaccines was performed on hospitalized children with consolidated pneumonia. The effect of different number of vaccine doses was evaluated in 2008 and 2010 birth cohorts vaccinated with PCV7 and PCV13 respectively. The study aims to estimate the effects of PCV7 and PCV13 different number of doses on consolidated pneumonia, through the study of hospitalized children from 2008 and 2010 birth cohorts. Vaccination records of every child were available providing precise vaccination data;therefore a new approach was used to estimate PCVs effect. Incidence rate was calculated for each year of the study and for the different number of vaccine doses used each year. Exposure was calculated as person per year and rate ratio values determined the decrease of consolidated pneumonias. This decrease in percentage was estimated as the difference between the incidence with no vaccine and the incidence of every one of the doses. Incidence rate ratio revealed significant values for the three vaccine doses of PCVs for both cohorts. Upon comparing incidences, significant reduction percentages of consolidated pneumonia admissions were found. The reduction percentage of consolidated pneumonia for fully vaccinated (3 doses) patients was 69.3% and 84.6 % for PCV7 and PCV13, respectively. These results confirm that PCV7 and PCV13 are highly effective for reducing pediatric hospitalizations due to consolidated pneumonia, as reported by other national publications and demonstrated by international researchers.

Evaluating the efficacy of an attenuated Streptococcus equi ssp. zooepidemicus vaccine produced by multi-gene deletion in pathogenicity island SeseCisland_4

Streptococcus equi ssp. zooepidemicus(SEZ) is a pathogen associated with a wild range of animal species. Frequent outbreaks have occurred in recent years in pigs, horses, goats and dogs which is liable to infect humans. There is a lack of efficient vaccines against this disease and the occurrence of antibiotic resistance may render drug therapies ineffective. In this study, gene deletion mutant(ΔSEZ) in pathogenicity islands SeseCisland_4 was constructed. The mutant ΔSEZ had a 52-fold decrease in 50% lethal dose(LD_(50)) and had less capacity to adhere epithelial cells. Importantly, immunization of mice with attenuated vaccine ΔSEZ at the dose of 10~2 colony-forming units(CFU) mL^(–1) elicited a significant humoral antibody response, with an antibody titer of 1:12 800. Therefore, 10~2 CFU mL^(–1) might be used as the appropriate immune dose for the attenuated vaccine ΔSEZ, which provided mice with efficient protection against virulent SEZ. In addition, the hyperimmune sera against 10~2 CFU m L–1 attenuated vaccine ΔSEZ could confer significant protection against virulent SEZ infection in the passive immunization experiment and exhibited efficient bactericidal activity in the whole blood assay. Meanwhile, no viable bacteria was detected in blood when mice were immunized with ΔSEZ at the dose of 10~2 CFU mL^(–1) via hypodermic injection. Thereafter, the mutant ΔSEZ at the dose of 10~2 CFU mL^(–1) could confer significant protection in mice and had less negative effects on host, which could be an effective attenuated vaccine candidate for the prevention of SEZ.

Immuno-Chemotherapy Using Repeated Vaccine Treatment Can Produce Successful Clinical Responses in Advanced Metastatic Melanoma

Advanced Stage IV and IIIc melanoma has a dismal survival, with or without, standard chemotherapy. New therapies are required to improve survival and reduce morbidity. Repeated vaccine dosing does not appear to have been explored, so Vaccinia Melanoma Cell Lysate (VMCL) vaccine repetitive therapy was tested, either alone, or combined with chemotherapy. 37 patients (31 Stage IV [M1a(6), b(7), c(18)] and 6 Stage IIIc) were studied using intra-dermal VMCL vaccine therapy. If disease progressed, vaccine was continued with standard chemotherapy (DTIC and/or Fotemustine). Overall survival was assessed and clinical responses were also recorded. From vaccine commencement, median overall follow-up was 10 months. Survivals ranged from 4 to 73 months. Median (mean) overall survival was 10 (23.5) months;overall survival at 1, 2 and 3 years was 40.5%, 21.6% and 10.8% respectively. CR and PR occurred in 18.9% (7) and 18.9% (7) of patients;these were durable for up to 6.1 years in 4 patients. Stable disease was noted in a further 17 patients (45.9%). In 6 patients (16.2%) no response to therapy was apparent. Repeated vaccinations with or without chemotherapy produced strong, durable clinical responses with overall survival > 23 months occurring in nearly 25% of advanced melanoma patients. The overall disease control rate (CR, PR and SD) was 83.7%, including CR in very advanced cases. These results, in a largely unselected population of advanced metastatic melanoma patients, compare very favourably with other regimens, and notably were associated with minimal, if any, toxicity. Further analysis of this approach appears warranted.

Senegal Kicks Off Vaccination The inoculation campaign in Senegal starts off well with arrival of Chinese vaccines

On February 17,Senegal received 200,000 vaccines from the Chinese company Sinopharm.The vaccine offered a breath of relief to a country severely hit by the COVID-19 pandemic.Senegalese President Macky Sall personally traveled to the Blaise Diagne International Airport in Diass to receive the doses.

Effectiveness of BNT162b2 Vaccine against Critical Covid-19 in Adolescents

Background:The increasing incidence of pediatric hospitalizations associated with coronavirus disease 2019(Covid-19)caused by the B.1.617.2(delta)variant of severe acute respiratory syndrome coronavirus 2(SARS-CoV-2)in the United States has offered an opportunity to assess the real-world effectiveness of the BNT162b2 messenger RNA vaccine in adolescents between 12 and 18 years of age.Methods:We used a case-control,test-negative design to assess vaccine effectiveness against Covid-19 resulting in hospitalization,admission to an intensive care unit(ICU),the use of life-supporting interventions(mechanical ventilation,vasopressors,and extracorporeal membrane oxygenation),or death.Between July 1 and October 25,2021,we screened admission logs for eligible case patients with laboratory-confirmed Covid-19 at 31 hospitals in 23 states.We estimated vaccine effectiveness by comparing the odds of antecedent full vaccination(two doses of BNT162b2)in case patients as compared with two hospitalbased control groups:patients who had Covid-19-like symptoms but negative results on testing for SARS-CoV-2(test-negative)and patients who did not have Covid-19-like symptoms(syndrome-negative).

Memory B cell repertoire from triple vaccinees against diverse SARS-CoV-2 variants

Omicron,the most heavily mutated SARS-CoV-2 variant so far,is highly resistant to neutralizing antibodies,raising unprecedented concerns about the effectiveness of antibody therapies and vaccines 1,2.We examined whether sera from individuals who received two or three doses of inactivated vaccine,could neutralize authentic Omicron.The seroconversion rates of neutralizing antibodies were 3.3%(2/60)and 95%(57/60)for 2-and 3-dose vaccinees,respectively.For three-dose recipients,the geometric mean neutralization antibody titre(GMT)of Omicron was 16.5-fold lower than that of the ancestral virus(254).We isolated 323 human monoclonal antibodies(mAbs)derived from memory B cells in 3-dose vaccinees.

Optic neuritis after mRNA vaccination against COVID-19:a secondary analysis of post-approval national safety data by the Japanese government

Vaccination is the mainstream measure against coronavirus disease 2019(COVID-19).As of May 2022,more than 80%of the Japanese population has received vaccination doses(1),and booster vaccination programs are in progress.Acute disseminated encephalomyelitis is the most common type of demyelination following vaccinations,and although an increase in neuromyelitis optica spectrum disease(NMOSD)has recently been reported worldwide(2-4),no collective data,especially after newly developed mRNA vaccines against COVID-19,have been reported yet.

基于深圳市多起校园聚集性疫情的2剂次水痘疫苗保护效果分析

目的 评估校园水痘聚集性疫情现场2剂次水痘疫苗免疫程序的保护作用,为水痘的防控提供参考。方法 以2020-2022年深圳市盐田区报告水痘聚集性疫情的学校为调查现场,按照回顾性队列研究的方法分析水痘疫苗接种情况与水痘发病的关系。对不同规模的疫情进行异质性检验,计算2剂次水痘疫苗相对保护效果(relative vaccine effectiveness, rVE)的合并效应量。结果 共纳入校园水痘聚集性疫情12起,其中中学1起,小学9起,幼儿园2起,疫情规模为4~19例/起。水痘病例共124例,水痘罹患率为8.60%,其中突破病例占58.87%。1剂次水痘疫苗接种率为52.08%,2剂次接种率为30.31%,1剂次突破感染率(8.66%)高于2剂次(1.83%),差异有统计学意义(χ^(2)=22.309,P<0.001)。异质性检验结果显示,不同校园疫情的水痘疫苗保护效果无异质性(χ^(2)=2.403,P=0.998;I2=0.007%)。采用固定效应模型,以接种1剂次水痘疫苗为参照组,接种2剂次疫苗rVE的合并效应量73.75%(95%CI:50.30%~86.13%)。亚组分析,2剂次水痘疫苗接种0~<3年、3~<6年和≥6年的rVE呈下降趋势,分别为81.48%、71.62%和67.13%。结论 接种2剂次水痘疫苗的保护效果优于1剂次,可有效降低校园水痘聚集性疫情中学生感染水痘的风险。

Safety,immunogenicity and protective effect of sequential vaccination with inactivated and recombinant protein COVID-19 vaccine in the elderly:a prospective longitudinal study

The safety and efficacy of COVID-19 vaccines in the elderly,a high-risk group for severe COVID-19 infection,have not been fully understood.To clarify these issues,this prospective study followed up 157 elderly and 73 young participants for 16 months and compared the safety,immunogenicity,and efficacy of two doses of the inactivated vaccine BBIBP-CorV followed by a booster dose of the recombinant protein vaccine ZF2001.The results showed that this vaccination protocol was safe and tolerable in the elderly.After administering two doses of the BBIBP-CorV,the positivity rates and titers of neutralizing and anti-RBD antibodies in the elderly were significantly lower than those in the young individuals.After the ZF2001 booster dose,the antibody-positive rates in the elderly were comparable to those in the young;however,the antibody titers remained lower.Gender,age,and underlying diseases were independently associated with vaccine immunogenicity in elderly individuals.The pseudovirus neutralization assay showed that,compared with those after receiving two doses of BBIBP-CorV priming,some participants obtained immunological protection against BA.5 and BF.7 after receiving the ZF2001 booster.Breakthrough infection symptoms last longer in the infected elderly and pre-infection antibody titers were negatively associated with the severity of post-infection symptoms.The antibody levels in the elderly increased significantly after breakthrough infection but were still lower than those in the young.Our data suggest that multiple booster vaccinations at short intervals to maintain high antibody levels may be an effective strategy for protecting the elderly against COVID-19.

多纹钱蝶鱼源海豚链球菌的分离鉴定及灭活疫苗的免疫效果

为探究养殖的多纹钱蝶鱼(Selenotoca multifasciata)病害频发的原因,建立有效的病害防控方法,对暴发于海南养殖场的多纹钱蝶鱼病害开展调查并进行灭活疫苗的研制及免疫保护效果评估。分离到2株病原菌LSSM和DFSM,经形态学和16S rDNA序列分析,将病原鉴定为海豚链球菌(Streptococcus iniae)。将这2株菌与实验室收集保藏的2株鱼源海豚链球菌(菌株GXTO和GXAS)进行了血清型鉴定和耐药性、致病性分析,制备了灭活疫苗并评价了疫苗的免疫保护效果。研究表明:4株海豚链球菌鉴定为血清Ⅰ型。所有菌株均对青霉素类、头孢类、四环素等23种抗生素高度敏感、对丁胺卡那耐药,其中海南株LSSM、DFSM对庆大霉素和卡那霉素抗生素耐药,广西株GXTO和GXAS对庆大霉素和卡那霉素敏感。DFSM、GXTO和LSSM对多纹钱蝶鱼的半数致死量(LD_(50))分别为7.20×10^(2)、2.72×10^(3)和3.40×10^(6) CFU/尾,GXAS未显示毒力。分别制备3株毒株(DFSM、GXTO和LSSM)的灭活疫苗,通过腹腔注射途径免疫多纹钱蝶鱼,各组免疫鱼在同源菌株攻毒后,获得的免疫保护率分别为84.6%~85.7%、69.2%~71.4%和33.3%~40.0%;此外,DFSM免疫鱼在异源毒株LSSM和GXTO攻毒后,获得的交叉免疫保护率分别为86.7%和100%。本研究确定了海豚链球菌是海南养殖的多纹钱蝶鱼病害频发的病原,使用DFSM株制备的海豚链球菌灭活疫苗对多纹钱蝶鱼有良好的免疫保护效果。

Hesitancy to Receive the Booster Doses of COVID-19 Vaccine Among Cancer Patients in China:A Multicenter Cross-Sectional Survey—Four PLADs,China,2022

Summary What is already known about this topic?Cancer patients are more vulnerable and have higher mortality rates from severe acute respiratory syndrome coronavirus 2(SARS-CoV-2)than the general population;however,coverage for booster doses of the coronavirus disease 2019(COVID-19)vaccine was low among cancer patients in China.What is added by this report?Overall,32.0%and 56.4%of cancer patients from four Provincial Level Administrative Divisions(PLADs)expressed hesitancy toward the first and second booster doses,respectively.Factors negatively associated with hesitancy to receive booster doses included positive attitudes,perceived support,and higher exposure to COVID-19 vaccination information.Conversely,postvaccination fatigue was positively associated with vaccine hesitancy.What are the implications for public health practice?Improved COVID-19 vaccination coverage is needed to promote health for cancer patients.

Parotid swelling due to Hoshino strain following MMR vaccination in iranian immunization program

This paper reports two seronegative cases of parotid swelling following MMR vaccination,which contains Hoshino strain of mumps virus.This study showed a high,(5%) potential reactogenicity induced by Hoshino strain of current MMR vaccine administered in Iranian EPI.The rate of complication of parotid swelling following national immunization against mumps is more than natural infection.Based on the results of this report, there is the first report of occurrence of parotid swelling 31 days following MMR vaccination.This reaction or complication may not be dependent on the vaccine dose,because one of cases presented parotid swelling following taking one fifth of conventional dose of vaccine.It must be considered this strain may be with high rate of complication and be the subject of change of mumps strain of this vaccine in national immunization program of Iran.

山羊痘弱毒疫苗(AV41株)接种途径和剂量对牛抗体反应的影响

为评估山羊痘弱毒疫苗(AV41株)经皮下和皮内接种牛体后的抗体产生规律,优化牛体免疫程序,选取25头健康成年肉牛分为5组,每组5头,标准单头份剂量为含量1.0×10^(3.5)TCID_(50) AV41株,分别以5倍和10倍羊用剂量进行皮下和皮内免疫,于接种后0、15、30、45和60 d,利用病毒中和试验(VNT)和ELISA试剂盒检测血清抗体水平。结果显示:鼻咽拭子和血液PCR结果均为阴性,未出现排毒;VNT与ELISA抗体检测结果相似,免疫后第30天,皮下接种5倍剂量组中有60%牛抗体转阳,中和抗体滴度最高达1∶640。同时,皮内和皮下10倍剂量组各有40%牛抗体转阳,皮内5倍剂量组有20%牛抗体转阳。VNT中和指数与ELISA的S/P值呈现显著正相关。上述结果表明,类似于国际上相关疫苗的接种途径和剂量,皮下注射5倍羊头份剂量山羊痘弱毒疫苗是安全和有效的,可作为临床预防牛结节皮肤病的免疫接种方案。

定量药理学在疫苗研发中应用的概述与展望

本文从抗原提呈、佐剂、淋巴系统等方面介绍了疫苗的作用机制与产品特点,并总结了定量药理学的QSP、PK/PD、Dose-Response、MBMA等核心工具在疫苗研发的量效关系、临床前与临床转化、生物标记物与有效性相关性等研究中的关键应用。期待在药物研发中成功应用的模型引导药物开发理念能够在疫苗领域促成模型引导的疫苗研发,进而为更安全、有效、可控的疫苗产品研发做出其应有的贡献。

不同免疫剂量禽流感灭活疫苗对蛋种鸡产蛋率及抗体效价的影响

为评估不同免疫剂量禽流感灭活疫苗对父母代蛋种鸡产蛋率及抗体效价的影响,在河北省某海兰褐蛋种鸡场挑选产蛋稳定的720羽55周龄蛋种鸡,平均分为6组,每组4个重复,每个重复30羽;试验组分别胸部皮下注射0.2、0.3、0.5、0.7 mL/羽的重组禽流感病毒H5+H7三价灭活疫苗(H5N1 Re-11株+Re-12株,H7N9 Re-3株),同时设0.5 mL生理盐水组及不免疫空白对照组;统计免疫前及免疫后1~4周各组的产蛋率,并分别在免疫前及免疫后3、6、10、14周采血,检测其抗体水平。结果显示:免疫后2周,0.7 mL组产蛋率下降幅度最大,与对照组差异极显著(P<0.01),而0.2 mL组下降幅度最小,与对照组差异不显著(P>0.05)。各免疫组免疫后3周的H5N1 Re-11抗体水平与免疫前相比均显著上升(P<0.05),免疫后14周0.2 mL组与0.7 mL组抗体滴度最高,均为8.60log2;免疫后3周的H7N9 H7-Re3抗体水平与对照组相比均显著上升(P<0.05),且各免疫组间的上升幅度差异均不显著(P>0.05),免疫后14周,0.7、0.3、0.2 mL组的抗体滴度较高,均在7.60log2以上。结果表明,0.2 mL/羽的免疫剂量对蛋鸡产蛋性能影响最小,且诱导的抗体水平及其维持时间均与0.7 mL/羽相当,适于作为产蛋期禽流感的最佳免疫剂量。本研究为养鸡场产蛋期禽流感最适加强免疫剂量的选择提供了依据。