Conceived and designed the experiments: MW JY TL. Performed the experiments: MW JY TL Yang Liu Xi Chen XX Yanhui Liu Y. Wang JW BD EL KL Y. Wu PH. Analyzed the data: MW JY TL Xiongfei Chen JL. Contributed reagents/materials/analysis tools: JW BD EL KL Y. Wu PH. Wrote the paper: MW JY TL.
The authors have declared that no competing interests exist.
To evaluate the risk of the recurrence and the efficiency of the vaccination, we followed-up antibody responses in patients with the 2009 pandemic H1N1 influenza and persons who received the pandemic H1N1 vaccine in Guangzhou China.
We collected serum samples from 129 patients and 86 vaccinated persons at day 0, 15, 30, 180 after the disease onset or the vaccination, respectively. Antibody titers in these serum samples were determined by haemagglutination inhibition (HI) assay using a local isolated virus strain A/Guangdong Liwan/SWL1538/2009(H1N1).
HI antibody positive rate of the patients increased significantly from 0% to 60% at day 15 (χ2 = 78,
Vaccination of 2009 influenza A (H1N1) was effective. However, about half or more recovered patients and vaccinated persons might have lost sufficient immunity against the recurrence of the viral infection after half a year. Vaccination or re-vaccination may be necessary for prevention of the recurrence.
A pandemic influenza A (H1N1) virus spread worldwide since April 2009, resulting in more than 16,000 deaths until March 2010. On 10 August 2010, WHO Director-General Dr Margaret Chan announced that the H1N1 influenza virus has moved into the post-pandemic period
We investigated antibody responses in 129 patients with the pandemic influenza HIN1 and 86 persons who received the pandemic H1N1 vaccine in Guangzhou China. Patients who showed influenza symptoms, temperature ≥37.5° and viral RNA and/or antibody seroconversion for the pandemic virus were recruited in an outbreak of 2009 pandemic influenza H1N1 in a boarding school from August 21st to October 15th, while vaccinated study subjects were recruited from healthy persons who received the vaccine provided by Ministry of Health of China on October 30th 2009. These patients or vaccinated persons showed antibody negative to the pandemic virus (HI titer <1∶20) at the onset day of the disease or when they received the vaccination (day 0). Serum samples were collected from these patients and vaccinated persons at day 0, 15, 30, 180 after the onset of the disease or the vaccination, respectively. The ages of the study subjects in patient group were from 14 to 20 years, and that in vaccinated people were from 19 to 57 years. There are 86 males and 43 females in the patient group and 46 males and 40 females in vaccinated group.
The influenza A/H1N1 monovalent, split-virus, non-adjuvanted vaccines were manufactured by Tianyuan Bio-Pharmaceutical Co., Ltd. (batch number 20090902) through the nationwide vaccination program. Each dose of 0.5 ml product contained 15 µg hemagglutinin as prescribed by national guidelines. The vaccine was administered through intramuscular injection in the deltoid muscle.
This study was approved by the ethics committee of the Guangzhou Center for Disease Control and Prevention and written informed consent was obtained from the study subjects.
The existence of pandemic influenza H1N1/2009 virus was detected by real-time RT-PCR as described previously
Antibody titers in these serum samples were determined by haemagglutination inhibition (HI) assay as described previously
All the experiments were manipulated in the same laboratory of Guangzhou center for disease control and prevention.
Data were analyzed using EpiInfo version 3.3.2 (CDC, USA) and SPSS version 13.0 (SPSS Inc., USA). The statistically significant criterion was P-value <0.05. We compared the seroconversion rate (HI ≥40) by χ2-test between day 15 and day 30 or day 30 and day 180 or between natural infection and vaccinated group. We compared geometric mean titers (GMT) of those with positive results by Independent-Samples T test between day 15 and day 30 or day 30 and day 180 or between natural infection and vaccinated group. For GMT calculations, antibody levels below the detection limit (<1∶20) were assigned the value of 1∶10.
HI antibody positive rate of the patients increased significantly from 0% to 60% (95%CI: 26–88%) at day 15 (χ2 = 78,
Note: Detection limitation (HI titer <20) is indicated by the dotted line. Error bar indicates ± standard deviation (SD) from different individual study subjects. * indicates significant differences (
Group | total | positive rate | GMT | ||||||||
day15 | day30 | day180 | χ2 | day15 | day30 | day180 | T value | ||||
day15 vs day30 | day30 vs day180 | day15 vs day30 | day30 vs day180 | ||||||||
natural infection | 129 | 60 | 100 | 52 | 23 |
38 |
63 | 80 | 52 | 0.92 | 4.5 |
vaccination | 86 | 78 | 81 | 34 | 0.32 | 39 |
100 | 193 | 74 | 4.5 |
5.1 |
*p<0.05,
**p<0.01.
Age group | T15 | T30 | T180 | |||||||||||||||
total | Positive result | GMT | total | Positive result | GMT | total | Positive result | GMT | ||||||||||
No.Positive | Positive Rate% | 95%CI | GMT | 95%CI | No.Positive | Positive Rate% | 95%CI | GMT | 95%CI | No.Positive | Positive Rate% | 95%CI | GMT | 95%CI | ||||
19- | 30 | 26 | 87 | 69–96 | 131 | 81–159 | 30 | 25 | 83 | 65–94 | 184 | 121–280 | 28 | 12 | 43 | 25–63 | 76 | 56–101 |
30- | 22 | 17 | 77 | 55–92 | 98 | 69–139 | 22 | 19 | 86 | 65–97 | 207 | 118–361 | 21 | 3 | 14 | 3–36 | 127 | 47–343 |
40- | 24 | 17 | 71 | 49–87 | 94 | 68–130 | 24 | 20 | 83 | 63–95 | 204 | 146–286 | 23 | 9 | 39 | 20–62 | 69 | 48–98 |
50–60 | 10 | 7 | 70 | 34–93 | 80 | 47–135 | 10 | 6 | 60 | 26–88 | 160 | 72–355 | 10 | 4 | 40 | 12–74 | 57 | 30–107 |
No significant difference was found in GMT of HI antibodies in positive samples collected from the patients between 63 (95%CI: 30–135) at day 15 and 80 (95%CI: 68–93) at day 30 (T = 0.92,
The 2009 pandemic influenza A (H1N1) virus is a completely new infectious agent to human being. To investigate antibody dynamics which induced by natural infection or vaccination of the virus, we conducted this prospective study by following-up the infected patients and vaccinated people in the same city for six months.
Consistent with previous reports
In contrast with previous studies which reported that the positive rate and GMT in children or elder persons were usually lower than the other age groups
In this study, we first reported that both positive rate and GMT of antibodies to 2009 pandemic influenza A (H1N1) virus were decreased quickly in the patients and vaccinated persons. Antibody positive rates had been dropped down from 100% and 81% at day 30 to 52% and 34% at day 180, while GMTs were decreased from 80 and 193 at day 30 to 52 and 74 at day 180 in patients and vaccinated people, respective. The observation of low level antibody responses to the pandemic influenza viral infection and quick decrease of protective antibody levels may be able to explain why some pandemic influenza patients acquired a re-infection shortly as reported by Perez et al
We thank Dr Robert E. Fontaine, Expert Advisors to CFETP, for his valuable advice and guidance.