Efficacy of "Hong Kong" vaccine in preventing "England" variant influenza A in 1972

Age-seroprevalence curves for the multi-strain structure of influenza A virus

The relationship between age and seroprevalence can be used to estimate the annual attack rate of an infectious disease. For pathogens with multiple serologically distinct strains, there is a need to describe composite exposure to an antigenically variable group of pathogens. In this study, we assay 24,402 general-population serum samples, collected in Vietnam between 2009 to 2015, for antibodies to eleven human influenza A strains. We report that a principal components decomposition of antibody titer data gives the first principal component as an appropriate surrogate for seroprevalence; this results in annual attack rate estimates of 25.6% (95% CI: 24.1% - 27.1%) for subtype H3 and 16.0% (95% CI: 14.7% - 17.3%) for subtype H1. The remaining principal components separate the strains by serological similarity and associate birth cohorts with their particular influenza histories. Our work shows that dimensionality reduction can be used on human antibody profiles to construct an age-seroprevalence relationship for antigenically variable pathogens.

Antibody responses to influenza a H1N1 vaccine compared to the circulating strain in influenza vaccine recipients during the 2013/2014 season in North America

BACKGROUND

Influenza strain A/California/07/2009 H1N1 (H1N1-09) reemerged in 2013/2014 as the predominant cause of illness. We sought to determine if antigenic drift may have contributed to the decreased responses to influenza vaccine.

METHODS

Fifty adults who received trivalent inactivated influenza vaccine (IIV3) and 56 children who received live attenuated quadrivalent influenza vaccine (LAIV4) had hemagglutination inhibition (HAI) and microneutralizing (MN) antibodies measured in plasma against H1N1-09 and H1N1 2013/2014 (H1N1-14) influenza. Partial sequencing of the hemagglutinin gene (nt 280-780) was performed on 38 clinical isolates and the vaccine prototype.

RESULTS

In IIV3 recipients, HAI and MN titers against H1N1-14 were significantly lower than against H1N1-09 (p<0.0001 and 0.04, respectively). In LAIV4 recipients, only MN titers were significantly lower (p=0.02) for H1N1-09 compared with H1N1-14. A combined analysis showed significantly lower HAI and MN titers for H1N1-14 compared with H1N1-09 (p=0. 016 and 0.008, respectively). All 38 clinical isolates encoded the HA gene K166Q non-synonymous substitution; other non-synonymous substitutions were observed in <10% of the clinical isolates.

CONCLUSIONS

2013/2014 IIV3 and LAIV4 recipients had consistently lower MN antibody titers against H1N1-14 compared with H1N1-09. The HA K166Q mutation, located in a neutralizing epitope, probably contributed to these findings.

Immune Responses to Circulating and Vaccine Viral Strains in HIV-Infected and Uninfected Children and Youth Who Received the 2013/2014 Quadrivalent Live-Attenuated Influenza Vaccine

The live-attenuated influenza vaccine (LAIV) has generally been more efficacious than the inactivated vaccine in children. However, LAIV is not recommended for HIV-infected children because of insufficient data. We compared cellular, humoral, and mucosal immune responses to the 2013-2014 LAIV quadrivalent (LAIV4) in HIV-infected and uninfected children 2-25 years of age (yoa). We analyzed the responses to the vaccine H1N1 (H1N1-09), to the circulating H1N1 (H1N1-14), which had significant mutations compared to H1N1-09 and to B Yamagata (BY), which had the highest effectiveness in 2013-2014. Forty-six HIV-infected and 56 uninfected participants with prior influenza immunization had blood and nasal swabs collected before and after LAIV4 for IFNγ T and IgG/IgA memory B-cell responses (ELISPOT), plasma antibodies [hemagglutination inhibition (HAI) and microneutralization (MN)], and mucosal IgA (ELISA). The HIV-infected participants had median CD4+ T cells = 645 cells/μL and plasma HIV RNA = 20 copies/mL. Eighty-four percent were on combination anti-retroviral therapy. Regardless of HIV status, significant increases in T-cell responses were observed against BY, but not against H1N1-09. H1N1-09 T-cell immunity was higher than H1N1-14 both before and after vaccination. LAIV4 significantly increased memory IgG B-cell immunity against H1N1-14 and BY in uninfected, but not in HIV-infected participants. Regardless of HIV status, H1N1-09 memory IgG B-cell immunity was higher than H1N1-14 and lower than BY. There were significant HAI titer increases after vaccination in all groups and against all viruses. However, H1N1-14 MN titers were significantly lower than H1N1-09 before and after vaccination overall and in HIV-uninfected vaccinees. Regardless of HIV status, LAIV4 increased nasal IgA concentrations against all viruses. The fold-increase in H1N1-09 IgA was lower than BY. Overall, participants <9 yoa had decreased BY-specific HAI and nasal IgA responses to LAIV4. In conclusion, HIV-infected and uninfected children and youth had comparable responses to LAIV4. H1N1-09 immune responses were lower than BY and higher than H1N1-14, suggesting that both antigenic mismatches between circulating and vaccine H1N1 and lower immunogenicity of the H1N1 vaccine strain may have contributed to the decreased H1N1 effectiveness of 2013-2014 LAIV4.

Double-blind, randomized study of the effects of influenza vaccination on the specific antibody response and clinical course of patients with chronic fatigue syndrome

OBJECTIVE

To determine whether influenza immunization is associated with early side effects, a deleterious impact on the illness course and depressed antibody response in patients with chronic fatigue syndrome (CFS).

DESIGN

Prospective, randomized, double-blind, placebo controlled trial. CFS patients and healthy volunteers filled out a questionnaire on immunization side effects and had hemagglutination-inhibiting (HI) antibody titres measured pre- and three weeks after immunization. CFS patients completed symptom and function questionnaires before and during the six-week, postimmunization period.

SETTING

Ambulatory care.

POPULATION STUDIED

Convenience sample of 40 CFS patients fulfilling the Centers for Disease Control and Prevention criteria and 21 demographically matched healthy volunteers.

INTERVENTIONS

CFS patients were randomly selected to receive commercially available whole virus influenza vaccine (n=19) or an injection of saline placebo (n=21). Healthy volunteers received vaccine only.

MAIN RESULTS

As a group, immunized CFS patients had lower geometric mean HI antibody rises than healthy volunteers (P<0.001). However, there was no difference in the rates of fourfold titre rises, and immunization did achieve a probably protective titre (1:32 or greater) in most CFS patients. No difference could be detected between immunized and placebo CFS patients in immunization side effects, although CFS patients as a group reported four times as many side effects as healthy volunteers. Further, in the six weeks following immunization, placebo and immunized CFS patients did not demonstrate any differences in terms of functioning, symptom severity and sleep disturbance.

CONCLUSIONS

In patients with CFS, influenza immunization is safe, not associated with any excess early reactions, and stimulates an immunizing response comparable with that of healthy volunteers.

Effect of 25-hydroxyvitamin D status on serological response to influenza vaccine in prostate cancer patients

BACKGROUND

Epidemiologic data suggest that there is an association between vitamin D deficiency and influenza infection. We conducted a prospective influenza vaccination study to determine the influence of vitamin D status on serological response to influenza vaccine in prostate cancer (CaP) patients.

METHODS

During the 2006-2007 influenza season, CaP patients treated at Roswell Park Cancer Institute were offered vaccination with the trivalent influenza vaccine (Fluzone®, 2006-2007) and sera collected for hemagglutination inhibition (HI) assay titers before and 3 months after vaccination. Response to vaccination was defined as ≥1:40 titer ratio or a fourfold increase in titer at 3 months, against any of the three strains. Serum 25-hydroxyvitamin D (25-D₃) levels were measured using DiaSorin ¹²⁵I radioimmunoassay kits.

RESULTS

Thirty-five patients with CaP participated in the study. Median baseline 25-D₃ level was 44.88 ng/ml (range: 9.16-71.98 ng/ml) Serological response against any of the three strains was noted in 80%. There was a significant effect of baseline 25-D3 level when tested as a continuous variable in relation to serological response (P = 0.0446). All patients in the upper quartile of 25-D3 level responded by mounting a serological response (P = 0.0344). None of the other baseline variables (age, race, chemotherapy status, or white cell count) had an effect on serological response.

CONCLUSIONS

In this study in CaP patients, a replete vitamin D status was associated with more frequent serological response to influenza vaccine.

Influenza vaccination: is it appropriate in chronic fatigue syndrome?

Chronic fatigue syndrome (CFS) is a recognized clinical illness of unknown cause and pathophysiologic mechanisms. Immunizing patients against influenza would seem to be a prudent strategy since infection has been associated with symptom exacerbation. However, patients with CFS have demonstrated variable abnormalities in the immune system, the clinical significance of which is unclear. Anecdotal information has suggested that, due to the etiologic uncertainty surrounding CFS, many patients reject immunization, fearful of untoward effects. This article attempts to clarify the situation by reviewing immunologic findings in CFS and influenza vaccines in current use. Results from a recent survey of perceptions of patients with CFS regarding immunization revealed that 31% felt immunization was neither safe nor beneficial. This opinion was universal in those patients who had never received influenza vaccine. Among patients who had received vaccine and experienced an adverse effect, 26% felt the vaccine was safe and 28% felt it was beneficial. Among those who had received vaccine without an adverse effect, 45% believed the vaccine was safe, and 55% felt it was effective. CFS patients as a group expressed concern that influenza vaccine would alter an already dysfunctional immune system, or worsen CFS symptoms. Significantly more patients with CFS who had never received influenza vaccine voiced this opinion than did patients who had received immunization for influenza in the past. Contrary to the opinions expressed by the sample, clinical trials in CFS have yet to find that any type of immunization has produced a deleterious effect on symptoms or functioning. Moreover, patients with CFS in a randomized, placebo-controlled, double-blind trial of influenza immunization produced an antibody titer in the protective range to inactivated trivalent influenza vaccine, although the geometric mean titer was slightly blunted compared with healthy vaccinees. Although patients with CFS in placebo and active groups reported four times the number of post-injection adverse effects of healthy vaccinees, data re-analysis revealed that this finding was related to the overlap of common, post-influenza immunization symptoms and CFS constitutional symptoms. CFS is a poorly understood illness and some patients may believe in causal theories that lead to the rejection of disease prevention strategies such as immunization. However, influenza immunization appears to provide protective antibody levels without worsening CFS symptoms or causing excessive adverse effects. Efforts to motivate patients with CFS to obtain annual influenza immunization should take into account illness perceptions and concentrate on education based on placebo-controlled trials.

The pathogenesis and management of influenza virus infection in organ transplant recipients

Infection with influenza viruses poses specific problems in adult and pediatric organ transplant recipients, including a higher rate of pulmonary and extra-pulmonary complications. Also, data suggest that influenza is associated with acute cellular rejection and chronic allograft dysfunction. The main strategy of influenza prevention has been influenza immunization in order to stimulate local and systemic antibodies. However, studies have shown that antibody response to inactivated influenza vaccine is decreased in all groups of organ transplant recipients. A live attenuated influenza virus vaccine is nearing approval in the United States. However, studies are needed in organ transplant recipients to determine whether the live attenuated influenza virus vaccine can enable these patients to mount a protective immune response and what degree of protection or amelioration of illness is provided by such vaccine. It is also important to verify the safety of this vaccine in organ transplant recipients because live virus may cause severe disease in these patients. Therefore, other modalities of prevention against influenza, such as chemoprophylaxis with antiviral drugs, should be considered in this patient population. The current review provides an overview of the incidence, clinical manifestations, and strategies for the prevention and management of influenza in organ transplant recipients.

Influenza virus infection in adult solid organ transplant recipients

BACKGROUND

Solid organ transplant (SOT) recipients have been reported to be more susceptible to influenza virus. However, little is known about the clinical epidemiology and the implications of influenza viral infection among SOT recipients.

METHODS

Cohort study of influenza viral infection in SOT recipients at the University of Pittsburgh Medical Center.

RESULTS

Between November 1990 and April 2000, 30 cases of influenza were diagnosed in SOT recipients at our center, including influenza A (n = 22) and influenza B (n = 8). These included recipients of lung (n = 19), liver (n = 5) and kidney (n = 6) transplants. The incidence of influenza viral infection was 41.8 cases/1,000 person years (PYs), 2.8 cases/1000 PYs and 4.3 cases/ 1,000 PYs among lung, liver and renal transplant patients, respectively (p <0.0001). Symptoms were reported in all patients and included malaise, myalgia/ arthralgia, fever, cough, and shortness of breath. Secondary bacterial pneumonia occurred in five patients (17%). Other complications were seen in three SOT recipients (2 liver and 1 kidney) and included: myocarditis, myositis, and bronchiolitis obliterans. Biopsy of the transplanted organ was performed in 21 SOT recipients (18 lung, 1 liver and 2 kidney) at the time of influenza viral infection. Overall, 62% (13/21) showed variable degrees of acute allograft rejection, and included 61% (11/18) of lung, and 100% (2/2) of kidney transplant recipients.

CONCLUSIONS

Influenza infection is associated with significant morbidity in different groups of SOT recipients. Studies are needed to determine if yearly chemoprophylaxis with antiviral drugs might benefit this patient population.

The subclass IgG responses of mice to influenza surface proteins formulated into liposomes

Unprimed mice and mice primed by prior infection with an H1N1 subtype of influenza virus were used to assess the total and subclass IgG serum antibody responses to influenza virus A/Sichuan/2/87 (H3N2) surface haemagglutinin and neuraminidase proteins incorporated into four different formulations of liposomes. Only one of these liposome preparations, DSPC(B), induced greater total IgG, and subclass IgG1 and IgG2a antibody levels, in sera from both primed and unprimed mice than the aqueous A/Sichuan surface preparations alone administered at equivalent levels of haemagglutinin protein. The same DSPC(B) liposome formulation of A/Sichuan antigens was also the only preparation found to elicit levels of IgG2b and IgG3 subclass antibodies above baseline values in these animals.

An outbreak of influenza A (H3N2) in a well immunized nursing home population

OBJECTIVE

To describe the epidemiologic features of an outbreak of influenza A that occurred in a skilled nursing home although over 90 percent of the resident population had previously received influenza vaccine.

DESIGN

Retrospective cohort study.

SETTING

Skilled nursing home facility in western New York State.

PATIENTS

Nursing home residents and patient-care staff.

MAIN OUTCOME MEASURE

Incidence of influenza-like illness among vaccinated versus unvaccinated nursing home residents and staff.

RESULTS

Thirty-seven of 124 residents (attack rate = 30%) and 18 of 146 staff (attack rate = 12%) had an influenza-like illness. Staff illness began 16 days prior to onset among residents. Six cases of pneumonia and three influenza-related deaths occurred, all among the vaccinated residents. Ninety percent of the nursing home residents and 10% of the staff received the influenza vaccine prior to the outbreak. The calculated vaccine efficacies were minus 21% and plus 45% for residents and staff, respectively.

CONCLUSION

While antigenic drift of the circulating influenza virus was the major factor in the apparent vaccine failure, the observed poor staff immunization rate (10%) and absence of surveillance which precluded the use of amantadine chemoprophylaxis suggest that the use of these strategies may be of importance in controlling influenza outbreaks in nursing homes.

Adverse reactions to amantadine prophylaxis of influenza in a retirement home

OBJECTIVE

Controversy exists about the safety of following the recommendation of the Immunization Practice Committee of the Centers for Disease Control that nursing home residents be given amantadine prophylaxis during influenza outbreaks. This study was undertaken to define the incidence of adverse reactions to amantadine in the elderly and to identify risk factors for side effects.

DESIGN

A retrospective cohort study.

SETTING

A retirement home which offered amantadine prophylaxis to its residents during a presumed influenza outbreak.

PARTICIPANTS

Of the 96 elderly residents, 79 accepted the offer of amantadine prophylaxis.

MAIN OUTCOME MEASURES

Attributable adverse health outcomes as assessed by chart review.

RESULTS

41% of the people receiving amantadine had attributable adverse reactions, of which 22% were classified as severe. Severe adverse reactions were associated with residence in the assisted living section of the facility (P = 0.002), a greater number of underlying diagnoses (P = 0.009), congestive heart failure (P = 0.02), and high serum creatinine (P = 0.02). A person with none of these risk factors had a 7% chance of having a severe adverse outcome compared to a 70% chance for someone with all four risk factors.

CONCLUSION

The findings raise concern that the prophylactic administration of amantadine to all elderly residents of nursing and retirement homes may be associated with a high incidence of unacceptable reactions, particularly among less healthy residents.

Enhancement of antibody responses to influenza B virus haemagglutinin by use of a new adjuvant formulation

Mice and guinea pigs were immunized with the haemagglutinin (HA) of influenza B-USSR/100 virus, either in Syntex Adjuvant Formulation-1 (SAF-1) or in saline. Antibody titres were determined by ELISA, haemagglutination inhibition and virus neutralization. Animals immunized with HA in SAF-1 had significantly higher antibody titres than did animals immunized with HA in saline. Both 3-week-old and 13 1/2-month-old mice had greater and more uniform antibody responses to HA in SAF-1 than to HA in saline.

Influenza vaccination in Australia: a review of the economic evidence for policy recommendations

The National Health and Medical Research Council recommends that persons who are believed to be at a higher risk of the complications and of dying of influenza should receive annual vaccinations against the disease. The Council refers specifically to persons who are over the age of 65 years and to those with chronic medical conditions. Recommendations such as these place demands on scarce health resources and it is important to determine if such policies result in the efficient utilization of resources. Accordingly, this article reviews the evidence on the economic efficiency of different vaccination strategies. Two major conclusions emerge. First, even allowing for variability in vaccine effectiveness due to viral antigenic drift, influenza-vaccination programmes, in general, are more cost-effective than are many other interventions that are undertaken as a routine in Australia. Secondly, vaccinating healthy persons who are 45 years of age to 64 years of age is more cost-effective than is vaccinating persons in some of the high-risk groups. Thus, there is likely to be a case for reconsidering whether healthy persons who are younger than 65 years of age also should be included in the official recommendations.

Prevention and control of influenza. Role of vaccine

A major component in the prevention and control of influenza should be the use of killed influenza vaccines. These vaccines became possible after the first discovery of human strains of influenza virus in the 1930s. The ensuing decades have seen marked improvement in the available inactivated vaccines. Current vaccines have excellent reliability and assured potency, and they contain the proper antigens to match the frequent changes in circulating influenza viruses. Killed vaccines work by inducing serum antibodies against the hemagglutinin and neuraminidase of the vaccine strains, with sufficient antibodies ensuring protection against infection. The antibody responses to current vaccines appear to be adequate in all age groups. Although antibody responses are depressed in patients receiving chemotherapy or immunosuppressants, current vaccines do provide protection for most populations. Vaccines prevent the manifestations of disease by about 30 to 70 percent in all populations, and they reduce deaths in high-risk individuals by about 60 to 87 percent. Local adverse reactions to vaccine are quite common, but not severe. Fever, also somewhat common, usually does not last beyond 48 hours. Neurologic complications have not been observed since the use of the swine influenza vaccine of 1976. Killed vaccines should be given annually in the fall, but they can be given up to and during an outbreak. Target groups for vaccines have been defined by the Centers for Disease Control. In recent years, these groups have included physicians and nurses who give care to patients at risk for complications of influenza.

An outbreak of influenza A in a nursing home

An outbreak of influenza A occurred in an elderly population in a Maryland nursing home between December 8, 1980 and January 13, 1981 and involved 76 of the 170 residents. Throat swabs from two of 10 acutely ill residents yielded influenza A virus similar to the A/Taiwan/1/79 strain. Fourfold or greater increases in the titer of complement-fixing (CF) or hemagglutination-inhibiting (HI) antibodies were detected in paired sera from four of five ill residents and from none of four well residents. One hundred (62.9 per cent) of 159 residents with known vaccination histories had been vaccinated with trivalent influenza virus vaccine in October and November 1980. Crude illness attack rates and mortality rates were similar in vaccinees and nonvaccinees. Various risk factors and hypotheses were examined in an attempt to explain the apparent lack of vaccine efficacy.

Antibody response to influenza immunization in adult patients with malignant disease

Eight-two patients with solid tumors and lymphomas were immunized with New Jersey, Hong Kong, and Victoria influenza vaccines. Patients were divided into groups according to treatment: chemotherapy, radiotherapy, or no treatment. Four parameters were examined to assess the response to immunization: seroconversion, protective titer level, geometric mean titer, and response to multiple vaccines. Patients with lymphoma showed the lowest antibody response. Patients with solid tumors had antibody responses which were not significantly different from controls but were superior to lymphoma patients (p less than .01). Timing of chemotherapy, immunoglobulin levels, and lymphocyte counts did not appear to play a major role in determining the antibody response. Patients with neoplastic diseases should be immunized against the prevailing influenza virus. Patients with lymphoma should also receive antiviral prophylactic therapy during influenza epidemics.

The influence of chemotherapy on response of patients with hematologic malignancies to influenza vaccine

Bivalent influenza vaccine (containing antigens A/Victoria and A/New Jersey) was administered to 52 patients with hematologic malignancies, and pre- and postvaccination antibody titers to both antigens were determined by hemagglutination-inhibition. In comparison to healthy controls, mean antibody titer elevations were lower for both antigens in all disease groups, being significant (p less than 0.05) for A/Victoria in patients with non-Hodgkin's lymphoma, acute leukemia and lymphoproliferative diseases, and for A/New Jersey in patients with Hodgkin's and non-Hodgkin's lymphomas. In comparison to controls, significant depression of antibody response to both antigens was seen in patients on combination chemotherapy (p less than 0.0005), to a lesser extent in patients on daily single alkylating agent chemotherapy (p less than 0.05), while untreated patients did not differ significantly. Lymphopenia and depressed immunoglobulin levels were associated with a higher failure rate in eliciting "protective" greater than or equal to fourfold antibody titer increases. The findings suggest that patients with hematologic malignancies who are receiving chemotherapy at the time of vaccination are unlikely to attain seroconversion to protective antibody levels with influenza vaccine.

Immunity to challenge in volunteers vaccinated with an inactivated current or earlier strain of influenza A(H3N2)

Volunteers were inoculated with vaccine made from the 30c mutant, A/Port Chalmers/73 or B/Hong Kong/8/73. Preliminary experiments showed that the 30 c strain was antigenically quite close to A/HK/8/68. Volunteers given 30c developed haemagglutination inhibiting antibodies against the 'current' 1973 serotypes (as well as to the vaccine virus) but the titres were less than those after the A/PC/73 vaccine. Volunteers were then challenged with a live attenuated virus, WRL 105, with A/Finland/4/74 antigens, by intranasal inoculation. The rates of infection were 43% after B/Hong Kong/8/73, 20% after 30c and 5% after A/PC/73. This indicated that the 30c gave some protection but that the vaccine prepared from the current strain gave more.

Immunity to attenuated influenza virus WRL 105 infection induced by heterologous, inactivated influenza A virus vaccines

Groups of student volunteers were immunized with one of five different inactivated influenza virus vaccines. The concentration of virus in the various vaccines differed by both the international unitage test and by the concentration of haemagglutinin, as measured by the single radial diffusion test; the results of the two methods of standardization showed no correlation. The serum HI response to immunization was variable; volunteers given A/England/72 showed a 16.6-fold increase in homologous serum antibody titre whilst volunteers given A/Hong Kong/68 vaccine showed a 4.2-fold increase. The variable response of volunteers to immunization could not be explained by the varied concentration of virus in the vaccines, as measured by either test, the titres of serum HI antibody present before immunization, or a combination of these two factors.The ability to infect volunteers with WRL 105 virus 4 weeks after immunization with heterologous, inactivated virus vaccine was directly related to the degree of cross-reactivity between the haemagglutinins of this vaccine virus and WRL 105 virus. Thus, the greatest number of infections by the challenge virus were seen in volunteers given A/Hong Kong/68 vaccine, less were observed in volunteers given A/England/72 vaccine, and least were found in groups given A/Port Chalmers/73 or A/Scotland/74 vaccine. However, compared with the incidence of infection in volunteers given B/Hong Kong/73 vaccine, all the heterologous influenza A vaccine gave some immunity to challenge infection.

The response to inactivated influenza A (H3N2) vaccines: the development and effect of antibodies to the surface antigens

A controlled trial of influenza vaccines in a boys' public school from November 1970 to October 1975 provided an opportunity to study the response to vaccine and the effect on subsequent natural challenge in boys with differing natural experience of influenza A strains. The response to influenza A (H3N2) vaccines was assessed by estimating homotypic and heterotypic antibodies to the surface antigens. Previous natural experience of influenza A was found to influence vaccine response and the effect of natural challenge. The antibody response to revaccination with the same strain showed a progressively poorer response to second and third doses. The protectitive effect of naturally acquired and vaccine-induced antibodies was assessed during two outbreaks of influenza A which occurred in the trial period.

Vaccination in the control of influenza

Although killed influenza vaccine given by injection is protective, able to reduce sickness absence in industry and to control influenza in the armed forces, it has not so far been possible to demonstrate more than a small effect on the disease in otherwise healthy adults in industry and offices in the United Kingdom. The reasons are probably the poor rate of acceptance of vaccine, the relatively low incidence of clinical influenza in most years, and the incomplete protection given by the vaccine. Until major epidemics can be accurately forecast it is suggested that influenza vaccination may most usefully be used on a selective basis, namely for protecting those with illness predisposing to a severe effect from influenza; persons in institutions such as schools and homes for the elderly; key workers in the general population; and persons over the age of 65 years among whom considerable mortality occurs in winters when influenza is prevalent.

Influenza at Christ's Hospital: March, 1974

Boys in a boarding-school given inactivated influenza-A or influenza-B vaccine have been observed during a simultaneous outbreak of influenza due to A/Port Chalmers, B/Hong Kong, and B/Intermediate strains. Influenza-B vaccine conferred substantial protection, the attack-rates in boys given B vaccine being 24% compared with 45% in a control group. A/Hong Kong vaccine, by preventing infection during the previous influenza A/England outbreak, left the boys vulnerable to influenza A/Port Chalmers. Influenza-A haemagglutination-inhibiting (H.I.) antibody acquired by natural infection was associated with more protection than H.I. antibody induced by vaccination. This difference was not seen with influenza-B H.I. antibody.

Clinical reactions and serologic response following inactivated monovalent influenza type B vaccine in young children and infants

A monovalent, zonally purified, inactivated influenza B vaccine was administered to 29 children, 3 to 6 years of age, and 16 infants, 12 to 28 months of age, as a single dose of 0.25 ml containing 250 chick cell agglutinating units. The vaccine was both antigenic and well tolerated in the older group of preschool children. In the infants the vaccine was also antigenic but poorly tolerated clinically. Febrile reactions to 102 or greater were seen in 9 of the 16 infants, and two of these infants experienced a seizure following vaccination. The clinical reactions observed with the administration of influenza B vaccine in the dose used in this study would suggest significant limitations on its use in children under 3 years of age.