Immunogenicity of the reduced-antigen-content dTpa vaccine (Boostrix(®)) in adults 55 years of age and over: a sub-analysis of four trials

Background

Older adults, especially those over 65 years, are at risk of more severe morbidity from diphtheria, tetanus and pertussis and may transmit pertussis to unvaccinated or not yet fully vaccinated infants, but data on their response to reduced-antigen-content tetanus, diphtheria and acellular pertussis (dTpa) vaccines are lacking.

Methods

A sub-analysis pooled immunogenicity results in 293 adults aged 55+ years (mean age 64.4 years) from four randomised, controlled clinical trials of dTpa vaccine (Boostrix^®, GlaxoSmithKline Biologicals) with or without IPV co-administration, or dTpa-IPV (Boostrix^® IPV).

Results

Seroprotective antibody levels were achieved by 82.8% for diphtheria and 94.5% for tetanus. For pertussis antigens, the booster response rate, defined as initially seronegative subjects [<5 EU/mL] reaching ≥5 EU/mL; or a ≥2-fold increase in antibody concentration if initially seropositive was 89.2% for pertussis toxoid, 95.8% for filamentous haemagglutinin and 94.5% for pertactin. Post-booster geometric mean concentrations (GMC) increased for all antigens. Post-booster anti-tetanus and anti-PRN GMCs tended to be higher in 55- to 64-year olds than in those aged 65+.

Conclusion

Larger numbers of subjects over 75 years are needed to better define responses in advanced age, but these data suggest that a single booster dose of dTpa or dTpa-IPV induces good immunological responses in most, and that these vaccines could be readily integrated into existing programmes.     

Booster vaccination of toddlers with reduced antigen content diphtheria–tetanus–acellular pertussis vaccine

Immunogenicity and reactogenicity of DTPa and reduced antigen dTpa booster vaccines were compared to a hepatitis A control vaccine in DTPa-primed toddlers aged 18–20 months. Post-booster, all DTPa and dTpa recipients were seroprotected against diphtheria and tetanus, and ≥93.3% had a booster response to pertussis. There were similar reactogenicity rates in the DTPa and dTpa vaccine recipients. Few Grade 3 symptoms were reported. Just over one in four children in the control group had diphtheria antibody at or potentially below the correlate of protection benchmark (0.016 IU/ml). Larger studies should evaluate potential benefits of reduced antigen vaccines and seroprotection in children who do not receive a booster dose of DTPa at this age, including protection against diphtheria until subsequent booster doses are given.     

Tolerability and antibody response in adolescents and adults revaccinated with tetanus toxoid, reduced diphtheria toxoid, and acellular pertussis vaccine adsorbed (Tdap) 4-5 years after a previous dose

Background

Although decennial adult boosters of tetanus and diphtheria toxoids are recommended in Canada and the United States, a second dose of pertussis vaccine is not currently recommended for adults.

Methods

This open-label, postmarketing, multicenter study evaluated the tolerability and immunogenicity of a second dose of an adult formulation of tetanus, diphtheria, and pertussis vaccine (Tdap) in adolescents and adults 5 years after a first dose.

Results

A total of 545 participants from previous Tdap vaccine studies, ranging in age from 15 to 69 years, participated in this study. Of these participants, 94.2% had at least one solicited adverse event after the booster dose such as injection-site erythema (28.6%), swelling (25.6%), or pain (87.6%) or a systemic adverse event such as myalgia (61.0%), headache (53.2%), malaise (38.2%), or fever (6.5%). These adverse events were slightly more frequent than after the initial dose. Postvaccination, 100% of participants had a tetanus antibody level ≥0.10 IU/mL and 95% had a diphtheria antibody level ≥0.10 IU/mL. For pertussis, 82.1% (pertussis toxoid), 96.7% (filamentous hemagglutinin), 95.6% (pertactin), and 99.8% (fimbriae) had a postvaccination antibody threshold of ≥50 EU/mL.

Conclusion

A second dose of Tdap vaccine 5 years after the initial dose was well tolerated and immunogenic in adolescents and adults.     

Immune responses in adults to revaccination with a tetanus toxoid, reduced diphtheria toxoid, and acellular pertussis vaccine 10 years after a previous dose

Background

Although decennial adult boosters of tetanus and diphtheria toxoids are recommended in Canada and the United States, a second dose of pertussis vaccine during adulthood is not currently recommended.

Methods

This open-label, multicenter study compared the safety and immunogenicity of a first dose of an adult formulation of tetanus, diphtheria, and acelluar pertussis vaccine (Tdap) with a repeat dose of Tdap in adults who had received Tdap 10 years previously.

Results

A total of 769 participants ranging in age from 20 to 72 years took part in this study; 92.3% of naïve and 92.7% of repeat-dose participants had at least one solicited adverse event. Injection-site pain (84.4% and 87.8%), erythema (29.7% and 23.1%), and swelling (23.3% and 20.5%), and myalgia (53.5% and 60.1%), headache (37.6% and 40.6%), malaise (29.0% and 29.4%), and fever (4.9% and 4.2%) were the most common solicited adverse events reported in the naïve and repeat-dose groups, respectively. Postvaccination antibody levels ≥0.1 IU/mL were achieved by 99.7% of the naïve-group participants and all of the repeat-dose participants for tetanus and 96.1% of the naïve group and 98.5% of the repeat-dose group for diphtheria, both meeting the predefined noninferiority criteria. For pertussis antibodies, anti-PT (89.2 EU/mL vs. 116 EU/mL) was higher in the repeat-dose group, anti-FHA (249 vs. 214) and anti-PRN (216 vs. 266) were similar, and anti-FIM (1015 vs. 779) was higher in the naïve group. Noninferiority criteria were met for all antigens except for anti-FIM.

Conclusion

A repeat dose of Tdap vaccine 10 years after the first dose was well tolerated and immunogenic in adults (ClinicalTrials.gov identifier: NCT00712959).     

Anti-diphtheria antibody seroprotection rates are similar 10 years after vaccination with dTpa or DTPa using a mathematical model

The reduced antigen content diphtheria, tetanus and pertussis (dTpa) vaccine (Boostrixtrade mark) has been shown to induce a strong booster response to all the vaccine components in 4-6 year olds. However, anti-diphtheria antibody levels were observed to be lower when compared to the "full strength" paediatric DTPa vaccine. To assess the impact of this difference on long-term protection, a mathematical model was developed to predict diphtheria antibody decay over time. The model was based on a linear decrease in log-transformed antibody concentrations after the first year post-vaccination. When applied to data collected 3.5 years after vaccination of 4-6 year olds with either DTPa or dTpa, the model predicted that 10 years post-vaccination, 98.6% of subjects vaccinated with dTpa were likely to remain seroprotected against diphtheria, compared to 99.6% vaccinated with DTPa. Therefore, the difference observed in diphtheria antibody geometric mean concentrations 1 month after booster vaccination at 4-6 years with dTpa or DTPa is unlikely to be of clinical relevance 10 years later at the time of the adolescent booster.     

Immunogenicity and safety of a booster dose of diphtheria,tetanus, acellular pertussis and inactivated poliomyelitis vaccine (Tdap-IPV; Repevax) administered concomitantly versus non-concomitantly with an influenza vaccine (Vaxigrip) to adults aged ≥60 years: An open-label,randomised trial

Background

Annual influenza vaccination provides an opportunity to administer a booster dose of diphtheria, tetanus, acellular pertussis and inactivated poliomyelitis vaccine (Tdap-IPV) to the elderly. This study evaluated immune responses to and safety of the two vaccines administered concomitantly or sequentially to elderly individuals in France and Germany.

Methods

Individuals aged ≥60 years who had received a diphtheria/tetanus booster within 5–15 years were randomised (1:1) to receive either Tdap-IPV and an inactivated influenza vaccine concomitantly (Group 1) or inactivated influenza vaccine then Tdap-IPV 28–35 days later (Group 2). Antibody titres were measured before and 28–35 days after each vaccination.

Results

The mean age of randomised individuals (n = 954) was 68.8 years. Post-vaccination seroprotection rates (≥0.1 IU/mL for diphtheria/tetanus and ≥8 1/dilution for polio) for Group 1 were non-inferior to Group 2 for diphtheria (85.4% vs. 87.5%), tetanus (both 100%), polio type 1 (99.8% vs. 100%), polio type 2 (both 100%) and polio type 3 (99.3% vs. 99.8%). Similarly, percentages of individuals with pertussis antibodies ≥5 EU/mL for Group 1 were non-inferior to Group 2: pertussis toxin (94.3% vs. 98.1%), filamentous haemagglutinin (99.8% vs. 100%), pertactin (97.3% vs. 96.0%), fimbriae 2 and 3 (91.7% vs. 89.5%). Post-vaccination geometric mean titres of anti-influenza haemagglutinin antibodies for Group 1 were non-inferior to Group 2. Adverse events following administration of Tdap-IPV were similar in both study groups, with no vaccine-related serious adverse events.

Conclusion

Tdap-IPV and inactivated influenza vaccine can be administered concomitantly in the elderly without impairing tolerability or the immune response to either vaccine.     

Vaccination of adults 65 years of age and older with tetanus toxoid, reduced diphtheria toxoid and acellular pertussis vaccine (Boostrix(®)): results of two randomized trials

Background

Pertussis can cause significant morbidity in elderly patients, who can also transmit this disease to infants and young children. There is little data available on the use of acellular pertussis vaccines in recipients ≥65 years of age.

Methods

Two studies examined the safety and immunogenicity of tetanus toxoid, reduced diphtheria toxoid, and acellular pertussis (Tdap) vaccine (Boostrix^®) in healthy ≥65 year olds. In Study A subjects received single doses of Tdap and seasonal influenza vaccine either co-administered or given one month apart. In Study B subjects received either Tdap or tetanus-diphtheria (Td) vaccine. Antibodies were measured before and one month after vaccination. Reactogenicity and safety were actively assessed using diary cards.

Results

A total of 1104 subjects 65 years of age and older received a Tdap vaccination in the two studies. In study A, no differences in immune responses to Tdap or influenza vaccine were observed between co-administered or sequentially administered vaccines. In study B, Tdap was non-inferior to Td with respect to diphtheria and tetanus seroprotection, and anti-pertussis GMCs were non-inferior to those observed in infants following a 3-dose diphtheria, tetanus and acellular pertussis (DTaP) primary vaccination series, in whom efficacy against pertussis was demonstrated. Reports of adverse events were similar between Tdap and Td groups.

Conclusions

Tdap was found to be immunogenic in subjects ≥65 years, with a safety profile comparable to US-licensed Td vaccine. Tdap and influenza vaccine may be co-administered without compromise of either the reactogenicity or immunogenicity profiles of the two vaccines.     

Anti-diphtheria antibody seroprotection rates are similar 10 years after vaccination with dTpa or DTPa using a mathematical model

The reduced antigen content diphtheria, tetanus and pertussis (dTpa) vaccine (Boostrix™) has been shown to induce a strong booster response to all the vaccine components in 4–6 year olds. However, anti-diphtheria antibody levels were observed to be lower when compared to the “full strength” paediatric DTPa vaccine. To assess the impact of this difference on long-term protection, a mathematical model was developed to predict diphtheria antibody decay over time. The model was based on a linear decrease in log-transformed antibody concentrations after the first year post-vaccination. When applied to data collected 3.5 years after vaccination of 4–6 year olds with either DTPa or dTpa, the model predicted that 10 years post-vaccination, 98.6% of subjects vaccinated with dTpa were likely to remain seroprotected against diphtheria, compared to 99.6% vaccinated with DTPa. Therefore, the difference observed in diphtheria antibody geometric mean concentrations 1 month after booster vaccination at 4–6 years with dTpa or DTPa is unlikely to be of clinical relevance 10 years later at the time of the adolescent booster.     

An open-label, randomized, multi-center study of the immunogenicity and safety of DTaP-IPV (Kinrix™) co-administered with MMR vaccine with or without varicella vaccine in healthy pre-school age children

Background

In the US, it is recommended that 4-6 year old children receive diphtheria-tetanus-acellular pertussis (DTaP), inactivated poliovirus (IPV), measles-mumps-rubella (MMR), varicella (V), and influenza vaccines. Data relating to the concomitant administration of combination DTaP-IPV vaccine (Kinrix™; GlaxoSmithKline Biologicals) and influenza or V vaccines are currently limited. This study was undertaken to evaluate the immunogenicity and reactogenicity of Kinrix™ when co-administered with MMR (M-M-RII^®, Merck & Co.) and Varivax™ (Merck & Co.) in 4-6 year old children.

Methods

Phase IIIb, open-label, non-inferiority study (NCT00871117). We randomized (1:1) healthy 4-6 year olds to receive Kinrix™ + MMR + V on day 0 (Group 1), or Kinrix™ + MMR on day 0, followed by V at month 1 (Group 2). We measured DTaP-IPV immunogenicity before and 1 month post-vaccination (prior to V vaccination in Group 2). We collected local and general solicited symptoms within 4 days after vaccination and serious adverse events (SAEs) through 6 months post-vaccination.

Results

We enrolled 478 subjects. One month post-vaccination, >95% of subjects in both groups had booster responses to diphtheria, tetanus and pertussis antigens and all subjects had seroprotective anti-poliovirus antibody titers. Immune responses in Group 1 were non-inferior to Group 2 for responses to DTaP-IPV antigens according to pre-specified criteria. Reporting of solicited local events at the DTaP-IPV site appeared to be similar between the two vaccine groups, as was reporting of solicited general adverse events within 4 days of vaccination; no vaccine related SAEs were reported.

Conclusion

Concomitant administration of varicella vaccine with Kinrix™ and MMR did not impact the immunogenicity of diphtheria, tetanus, pertussis or poliovirus antigens. Both vaccine regimens were well tolerated. These results support the co-administration of DTaP-IPV, MMR, and V vaccines in 4-6-year-old children, providing protection against multiple diseases in a timely and efficient manner.     

Immunogenicity and safety of one dose of diphtheria,tetanus, acellular pertussis and poliomyelitis vaccine (Repevax) followed by two doses of diphtheria,tetanus and poliomyelitis vaccine (Revaxis) in adults aged ≥40 years not receiving a diphtheria- and tetanus-containing vaccination in the last 20 years

Introduction

The immunogenicity and safety of one dose of Tdap-IPV (tetanus, diphtheria, acellular pertussis and inactivated poliomyelitis vaccine) and two doses of Td-IPV (tetanus, diphtheria and inactivated poliomyelitis vaccine) were assessed in adults who had not received a diphtheria- and tetanus-containing vaccine in the last 20 years.

Methods

This open-label, multicentre study was conducted in adults aged ≥40 years with no diphtheria- and tetanus-containing vaccine in the last 20 years. Participants received one dose of Tdap-IPV followed by two doses of Td-IPV (0, 1, 6 month schedule). Primary immunogenicity objectives: to demonstrate acceptable seroprotection rates (percentage of participants with antibody titre above threshold) post-dose 3 for diphtheria (≥0.1 IU/mL by seroneutralization assay [SNA]); tetanus (≥0.1 IU/mL by enzyme-linked immunosorbent assay [ELISA]); and poliomyelitis (≥8 1/dil by SNA); and to evaluate the percentage of participants with an antibody concentration ≥5 EU/mL (by ELISA) for pertussis antigens post-dose 1. Seroprotection rates were acceptable if the lower limit of the 95% confidence interval (CI) was >95%. Percentage of participants with basic clinical immunity against diphtheria (≥0.01 IU/mL) was also assessed. Safety (adverse events [AEs] and serious AEs) was assessed after each dose.

Results

Overall, 336 participants were included (mean age: 60.2 years). Post-dose 3 seroprotection rates were: diphtheria, 94.6% (CI 91.5–96.8); tetanus and poliomyelitis, 100% (CI: 98.8–100). Percentage of participants with an antibody titre ≥5 EU/mL against pertussis antigens was ≥95.8% for all five pertussis components. Basic clinical immunity against diphtheria was achieved in 100% (CI: 98.8–100) of participants. AEs were reported more frequently following vaccination with Tdap-IPV (post-dose 1: 65.3%) than with Td-IPV (post-dose 2: 48.3%; post-dose 3: 50.3%).

Conclusions

This study highlights the benefits of using Tdap-IPV followed by two doses of Td-IPV in an adult population to achieve maximal protection against diphtheria, tetanus, poliomyelitis and pertussis simultaneously.     

Assessment of safety and immunogenicity of two different lots of diphtheria, tetanus, pertussis, hepatitis B and Haemophilus influenzae type b vaccine manufactured using small and large scale manufacturing process

Background

Hib vaccine can be easily incorporated in EPI vaccination schedule as the immunization schedule of Hib is similar to that of DTP vaccine. To meet the global demand of Hib vaccine, SIIL scaled up the Hib conjugate manufacturing process. This study was conducted in Indian infants to assess and compare the immunogenicity and safety of DTwP-HB + Hib (Pentavac^®) vaccine of SIIL manufactured at large scale with the ‘same vaccine’ manufactured at a smaller scale.

Methods

720 infants aged 6-8 weeks were randomized (2:1 ratio) to receive 0.5 ml of Pentavac^® vaccine from two different lots one produced at scaled up process and the other at a small scale process. Serum samples obtained before and at one month after the 3rd dose of vaccine from both the groups were tested for IgG antibody response by ELISA and compared to assess non-inferiority.

Results

Neither immunological interference nor increased reactogenicity was observed in either of the vaccine groups. All infants developed protective antibody titres to diphtheria, tetanus and Hib disease. For hepatitis B antigen, one child from each group remained sero-negative. The response to pertussis was 88% in large scale group vis-à-vis 87% in small scale group. Non-inferiority was concluded for all five components of the vaccine. No serious adverse event was reported in the study.

Conclusions

The scale up vaccine achieved comparable response in terms of the safety and immunogenicity to small scale vaccine and therefore can be easily incorporated in the routine childhood vaccination programme.     

Immunogenicity of a combined diphtheria-tetanus-acellular pertussis vaccine in adults

Two clinical studies were undertaken to evaluate the immunogenicity of an adult-type dTpa booster vaccine (Boostrix by GlaxoSmithKline Biologicals). Blood samples taken prior to vaccination showed that 24.4 and 13.0% of subjects were seronegative for diphtheria and tetanus antibodies, respectively. Moreover, about one-third of the vaccinees had no detectable levels of antibodies to pertussis toxoid (PT) or pertactin (PRN). One month post-vaccination, more than 93% of all individuals, regardless of age or type of vaccine received, had seroprotective antibody levels for diphtheria and tetanus (> or = 0.1IU/ml). In those individuals vaccinated with the adult-type dTpa vaccine (Boostrix), more than 98% were found to be seropositive for antibodies to all three pertussis antigens (PT, filamentous haemogluttin (FHA), and PRN). These data suggest that immunity to diphtheria, tetanus and pertussis (DTP) in adults wanes and that booster vaccination with an adult-type combined dTpa vaccine would boost the serological response to diphtheria antitoxin, tetanus antitoxin and antibodies to Bordetella pertussis PT, FHA and PRN.     

The safety and reactogenicity of a reduced-antigen-content diphtheria-tetanus-acellular pertussis (dTpa) booster vaccine in healthy Vietnamese children

Despite effective infant immunization against pertussis, the disease continues to circulate due to waning immunity. Booster vaccinations against pertussis beyond infancy are widely recommended. In Vietnam, however, no recommendations for pertussis boosters beyond the second year of life exist. This open-label, single-centre study was designed to assess the safety of a single booster dose of reduced-antigen-content-diphtheria-tetanus-acellular-pertussis vaccine (dTpa) in 300 healthy Vietnamese children (mean age 7.9 years), who had completed primary vaccination against diphtheria, tetanus and pertussis. Solicited symptoms were recorded for 4 days and unsolicited and serious adverse events (SAEs) for 31 days post-vaccination. Pain and fatigue were the most common solicited local and general symptoms in 35.0% and 14.0% of children, respectively. Grade 3 swelling occurred in 3 children; no large injection site reactions or SAEs were reported. The dTpa booster vaccine was well tolerated and this study supports its administration in school age Vietnamese children.     

A comparative study to evaluate the safety and immunogenicity of two lots of Haemophilus influenzae type-B conjugate vaccine manufactured at different scales

Objective

To compare the immunogenicity and safety of two different lots of SII Haemophilus influenzae type-B-tetanus toxoid conjugate (SII HibP_RO) vaccine manufactured at different scales when given in 3-dose schedule.

Design

Phase IV, open label, comparative, randomized parallel group study.

Setting

Shirdi Sai Baba Hospital, Vadu Budruk, Pune and Pediatrics Department of King Edward Memorial Hospital Research Centre, Pune.

Subjects

204 normal healthy infants of age 6-8 weeks at the time of first vaccination.

Methods

The eligible subjects received 3 doses of 0.5 ml of SII HibP_RO vaccine of either lot depending upon randomization number, intramuscularly in right thigh in the EPI schedule of 6, 10 and 14 weeks. They also received concomitantly DTP-HB vaccine intramuscularly on left thigh and Oral Polio vaccine (OPV). Solicited reactions were captured for 7 days following each vaccination; the events beyond 7 days till day 28 were captured as unsolicited adverse events. Serious Adverse Events (SAEs) were looked for throughout the subject participation. Blood samples were collected at baseline (before the first dose) and one month after the third dose for anti-PRP (polyribosylribitol phosphate) antibodies.

Results

In both groups, more than 98% subjects achieved short-term seroprotection (anti-PRP ≥ 0.15 μg/ml) after 3 doses. The long-term seroprotection (anti-PRP ≥ 1 μg/ml) was 87% and 80% in infants receiving lot manufactured at industrial scale and small scale respectively. Short and long term seroprotection and GMTs increased significantly as compared to baseline in both the groups. Overall local pain (52% and 58%), redness (30% and 41%), swelling (34% and 44%), fever (6% and 6%) and irritability (52% and 50%) were reported in infants receiving lot manufactured at industrial scale and small scale respectively. Majority of the reactions were mild and resoled without any sequelae. Four SAEs, none of them causally related to the study vaccine, occurred during study.

Conclusion

SII HibP_RO vaccines manufactured in small and industrial scale are equally immunogenic, safe and confer adequate seroprotection to infants of 6-14 weeks of age. Scaling up production process has not affected the safety and immune response in the target population.     

Vaccination with 3-dose paediatric rotavirus vaccine (RotaTeq®): impact on the timeliness of uptake of the primary course of DTPa vaccine

Background

In countries like Australia where high coverage rates of early childhood vaccines has been achieved, ensuring timely vaccination is the next challenge – particularly where multiple doses are required for protection (e.g. DTPa vaccine). Since July 2007, for the first time, the Australian childhood vaccination schedule has included a vaccine (rotavirus vaccine) that must be administered within strict dosing windows.

Aim

To determine whether the introduction of a 3-dose rotavirus vaccine (RotaTeq^®) into the national childhood immunisation program in Victoria, Australia, had an impact on the timeliness of the primary course of DTPa vaccine that is also scheduled at the same ages (2, 4 and 6 months).

Study

We studied de-identified data of >17,000 children residing in four large and culturally diverse localities in the Eastern Region of Melbourne, Victoria who were born prior to or after the introduction of RotaTeq^® into the National Immunisation Program schedule. Timeliness was defined as the proportion of children who received a particular dose of DTPa vaccine within the dosing window for the equivalent dose of RotaTeq^®. We were particularly interested in any change in the timeliness of dose 3 of DTPa vaccine.

Results

Before the introduction of RotaTeq^®, timely uptake of doses 1 and 2 of DTPa vaccine was high (93–97%). However, timeliness of the 3rd dose was markedly lower, dropping to 80% in one locality. In the post-RotaTeq^® cohort, rates of timely uptake for doses 1 and 2 of DTPa vaccine remained high (97–99%). However, for DTPa vaccine dose 3, there was a clear trend toward improved timeliness – increasing by 5 to up to 12 percentage points compared with the pre-RotaTeq^® cohort.

Conclusion

Inclusion in the national immunisation schedule of the 3-dose vaccine RotaTeq^® that has strict dosing windows encourages parents to present in a timely fashion for their child's vaccination, which in turn may drive an improvement in timeliness of other concurrently scheduled vaccines (e.g. DTPa). Introduction of government-funded RotaTeq^® may improve the uptake of the crucial 3rd dose of DTPa vaccine, where traditionally the greatest delays are noted.     

Persistence of antibodies 3 years after booster vaccination of adults with combined acellular pertussis, diphtheria and tetanus toxoids vaccine

The duration of protection after vaccination with reduced antigen content diphtheria, tetanus and acellular pertussis vaccines (Tdap) is not known. Long-term post-vaccination serological data will help to improve understanding of the duration of humoral immunity and guide vaccination policy for the timing of repeat dose administration. The persistence of antibodies to Tdap antigens was measured 3 years after vaccination of adults 19-64 years of age with one of 2 Tdap vaccines (Boostrix^®, GlaxoSmithKline Biologicals; Tdap-B: or Adacel^®, Sanofi Pasteur; Tdap-A). In both groups, geometric mean concentrations for antibodies to diphtheria, tetanus, and pertussis vaccine antigens were decreased at year 3 relative to levels observed 1 month and 1 year following vaccination, but remained higher than pre-vaccination levels. Seroprotection rates for diphtheria and tetanus remained high for both Tdap vaccines (for diphtheria, 96.9% and 97.8% for the Tdap-B and Tdap-A groups, respectively; for tetanus, 98.1% and 99.6%, respectively).     

A randomised controlled trial with a diphtheria-tetanus-acellular pertussis (dTpa) vaccine in adults

The aim of this assessor-blinded trial was to compare the immunogenicity and reactogenicity of a candidate diphtheria, tetanus toxoids and acellular pertussis vaccine with reduced antigen content for diphtheria and pertussis (dTpa) with a licensed reduced adult-type diphtheria-tetanus vaccine Td (reduced diphtheria content) and with an experimental candidate monovalent acellular pertussis vaccine with reduced antigen content (pa). The dTpa and pa vaccines had identical pertussis antigen content. A total of 299 healthy adults (> or =18 years, mean age: 30.1 years+/-10.7) were randomised into 3 groups to receive a single dose of one of the study vaccines. In all groups, clinically significant reactions (severe) were infrequent (0-6%) and no serious adverse events were reported during the study. The incidence of local and systemic reactions following the administration of dTpa was comparable to the Td vaccine group. Of the total study group, prior to vaccination 52. 3 and 93.2% of the subjects had anti-diphtheria and anti-tetanus antibody levels > or = 0.1 IU/ml, respectively; and 73.1, 98.2 and 74.5% of the subjects were seropositive for pertussis toxin (PT), filamentous hemagglutinin (FHA) and pertactin (PRN) antibodies, respectively. One month after vaccination, a similar percentage of subjects in the dTpa and Td groups had anti-diphtheria (88.4% vs 90. 1%) and anti-tetanus (100% vs 98.9%) antibody levels > or =0.1 IU/ml. Similar anti-FHA (100%) and anti-PRN (98.9%) vaccine response rates were seen in the dTpa and pa groups, while the anti-PT vaccine response rates were 96.8 and 100.0%, respectively. The dTpa vaccine is as well tolerated and immunogenic as the licensed Td vaccine, and additionally, can also boost antibodies against pertussis.     

Barriers to early uptake of tetanus, diphtheria and acellular pertussis vaccine (Tdap) among adults-United States, 2005-2007

Background

The tetanus, diphtheria and acellular pertussis vaccine (Tdap) was recommended by the Advisory Committee on Immunization Practices (ACIP) for U.S. adults in 2005. Our objective was to identify barriers to early uptake of Tdap among adult populations.

Methods

The 2007 National Immunization Survey (NIS)-Adult was a telephone survey sponsored by the Centers for Disease Control and Prevention (CDC). Immunization information was collected for persons aged ≥18 years on all ACIP-recommended vaccines. A weighted analysis accounted for the complex survey design and non-response.

Results

Overall, 3.6% of adults aged 18-64 years reported receipt of a Tdap vaccination. Of unvaccinated respondents, 18.8% had heard of Tdap, of which 9.4% reported that a healthcare provider had recommended it. A low perceived risk of contracting pertussis was the single most common reason for either not vaccinating with Tdap or being unwilling to do so (44.7%). Most unvaccinated respondents (81.8%) indicated a willingness to receive Tdap if it was recommended by a provider.

Conclusions

During the first two years of availability, Tdap uptake was likely inhibited by a low collective awareness of Tdap and a low perceived risk of contracting pertussis among U.S. adults, as well as a paucity of provider-to-patient vaccination recommendations. Significant potential exists for improved coverage, as many adults were receptive to vaccination.     

Implementation of mandatory immunisation of healthcare workers: observations from New South Wales, Australia

Objective

To identify factors influencing implementation of a state-wide mandatory immunisation policy for healthcare workers (HCWs) in New South Wales (NSW), Australia, in 2007. Vaccines included were measles, mumps, rubella, varicella, hepatitis B, diphtheria, tetanus and pertussis, but not influenza.

Methods

We evaluated the first 2 years of this policy directive in 2009. A qualitative study was conducted among 4 stakeholder groups (the central health department, hospitals, health professional associations, and universities). 58 participants were identified using maximum variation sampling and data were analysed using a hierarchical thematic framework. Quantitative data on policy compliance were reviewed at the regional level.

Results

Success in policy implementation was associated with effective communication, including support of clinical leaders, provision of free vaccine, access to occupational health services which included immunisation, and appropriate data collection and reporting systems. Achieving high vaccine uptake was more challenging with existing employees and with smaller institutions.

Conclusion

These findings may apply to other jurisdictions in Australia or internationally considering mandatory approaches to HCW vaccination.     

Text message reminders to promote human papillomavirus vaccination

Objective

To implement and evaluate text message reminders for the second (HPV2) and third (HPV3) vaccine doses.

Design

Site-based intervention.

Setting

Nine pediatric sites (5 academic and 4 private) located in New York City.

Participants

Parents of adolescents 9-20 years who received HPV1 or HPV2 during the intervention period, January-June 2009.

Intervention

Parents who enrolled received up to three weekly text message reminders that their daughter was due for her next vaccine dose.

Outcome measure

On-time receipt of the next vaccine dose, within one month of its due date.

Results

During the intervention period, of 765 eligible HPV vaccine events, 434 enrollment instructions were distributed to parents (56.7% of doses). Parents of 124 adolescent girls (28.6% of those handed instructions) activated text message reminders. Comparing children of parents who enrolled versus those who did not, on-time receipt of next HPV vaccine dose occurred among 51.6% (95% CI 42.8-60.4%) versus 35.0% (95% CI 29.6-40.2%) of adolescents (p = .001). Similarly, among a historical cohort of adolescents, receiving HPV1 or HPV2 in the six months prior to the intervention period, on-time receipt of next vaccine dose was noted for 38.1% (95% CI 35.2-41.0%) (p = .003). Increases in receipt of next vaccine dose among intervention subjects were sustained at 4 months following the vaccine due date. Using a logistic regression model, after controlling for insurance and site of care, intervention subjects were significantly more likely than either control population to receive their next HPV vaccine dose on-time.

Conclusion

Among those choosing to enroll, text message reminders were an effective intervention to increase on-time receipt of HPV2 or HPV3.