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The acute phase serum samples from 284 confirmed measles cases, including 280 laboratories confirmed cases and 4 epidemiologically linked confirmed cases, were collected from 2013 to 2015. Of the total number of cases, 278 (97.89%) were collected in 2014. The age range for patients with confirmed measles cases in this study was between 0 and 58 years, with 262 (92.25%) cases in patients aged ≥ 20 years. Measles IgG avidity testing showed high avidity measles IgG antibodies in 172 (60.56%) cases, indicating a secondary immune response to measles (Table 1), while 80 (28.17%) cases showed low avidity measles IgG antibodies, indicating a primary immune response to a primary measles infection. High avidity was detected in only 21.43% of cases in patients aged < 1 year. The proportion of high avidity cases increased with age, being significantly higher in 70.07% of cases in patients aged 30–39 years (χ 2= 17.27, P = 0.002). Low avidity was detected at a significantly higher rate of 57.14% in patients aged < 1 year (χ2 = 12.26, P = 0.016).
Age groups (years) Cases No. (%) of MCV doses No. (%) Avidity testing classifications 0 1 ≥ 2 Unknown High avidity Equivocal Low avidity < 1 14 8 (57.14) 6 (42.86) 0 (0) 0 (0) 3 (21.43) 3 (21.43) 8 (57.14) 1–19 8 2 (25.00) 2 (25.00) 4 (50.00) 0 (0) 4 (50.00) 1 (12.50) 3 (37.50) 20–29 58 8 (13.79) 6 (10.34) 3 (5.17) 41 (70.69) 29 (50.00) 7 (12.07) 22 (37.93) 30–39 137 28 (20.44) 27 (19.71) 0 (0) 82 (59.85) 96 (70.07) 12 (8.76) 29 (21.17) ≥ 40 67 18 (26.87) 4 (5.97) 0 (0) 45 (67.16) 40 (59.70) 9 (13.43) 18 (26.87) Total 284 64 (22.54) 45 (15.85) 7 (2.46) 168 (59.15) 172 (60.56) 32 (11.27) 80 (28.17) Table 1. Measles IgG avidity testing results by age group
Overall, 64 (22.54%) patients had not been vaccinated, 52 (18.31%) had received at least a dose of MCV. The vaccination status for 168 patients (59.15%) was unknown, all of whom were aged ≥ 20 years (Table 1). Of the 52 measles cases with a vaccination history, 41 (78.85%) demonstrated high avidity, indicating SVF. This is a significantly higher proportion of high avidity cases than was observed among unvaccinated patients (χ2 = 10.23, P = 0.001) and patients with an unknown vaccination status (χ2 = 6.81, P = 0.009). Low avidity was demonstrated in 9 (17.31%) cases, indicating PVF. While a significantly higher proportion (39.06%) of those who had not been vaccinated showed low avidity (χ2 = 6.84, P = 0.033), only one patient who had received ≥ 2 doses of MCV demonstrated low avidity (Table 2).
No. of
MCV dosesCases No. (%) Avidity testing classifications High avidity Equivocal Low avidity 0 64 32 (50.00) 7 (10.94) 25 (39.06) 1 45 36 (80.00) 1 (2.22) 8 (17.78) ≥ 2 7 5 (71.43) 1 (14.29) 1 (14.29) Unknown 168 99 (58.93) 23 (13.69) 46 (27.38) Total 284 172 (60.56) 32 (11.27) 80 (28.17) Table 2. Measles IgG avidity testing results by MCV vaccination status
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All measles cases in this study presented with fever and rash. Cough was present in 61.54% of vaccinated patients, 76.56% of non-vaccinated patients, and in 80.95% of patients with unknown vaccination status. There were no significant differences in the presentation of coryza, conjunctivitis, and Koplik spots among three groups of patients, as classified by vaccination status (Table 3). In the 52 vaccinated patients, there was no significant difference in severity of clinical symptoms between high avidity and low avidity measles cases. Similarly, there were no significant differences in the presentation of cough, coryza, conjunctivitis and Koplik spots between high avidity and low avidity cases overall (Table 4). Regardless of vaccination status, clinical severity was significantly lower in high avidity measles cases than in low avidity measles cases (P < 0.001).
Symptoms Cases Vaccinated patients Unvaccinated patients Patients with unknown status Chi-square P No. % No. % No. % Fever 284 52 100.00 64 100.00 168 100.00 − − Rash 284 52 100.00 64 100.00 168 100.00 − − Cough 217 32 61.54 49 76.56 136 80.95 8.30 0.016 Coryza 132 17 32.69 32 50.00 83 49.40 4.87 0.088 Conjunctivitis 144 21 40.38 34 53.13 89 52.98 2.27 0.258 Koplik spots 115 17 32.69 28 43.75 70 41.67 1.69 0.429 Table 3. Clinical symptoms in measles cases classified by vaccination status
Symptoms Vaccinated patients All cases High avidity Low avidity Chi-square P High avidity Low avidity Chi-square P No. % No. % No. % No. % Cough 22 53.66 8 88.89 2.49 0.115 111 64.53 76 95.00 26.48 < 0.001 Coryza 10 24.39 5 55.56 2.09 0.148 57 33.14 54 67.50 26.16 < 0.001 Conjunctivitis 14 34.15 5 55.56 0.67 0.413 67 38.95 54 67.50 17.83 < 0.001 Koplik spots 10 24.39 5 55.56 2.09 0.148 52 30.23 44 55.00 14.20 < 0.001 Table 4. Clinical symptoms in high avidity and low avidity measles cases
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Of the 284 measles cases, the serum collection period was 0–24 days after rash onset. The median was 2 days and interval of quartiles (IQR) was 1–4 days. A positive measles IgM result was obtained in 76.06% (216) of cases. The positive measles IgM rate for high avidity and low avidity measles cases were 66.28% and 91.25%, respectively. The rate was significantly lower in high avidity measles cases (χ2 = 17.79, P < 0.001). When serum samples were collected on 0 day after rash onset, positive IgM rate only was 24.32% in high avidity measles cases, compared with 83.33% in low avidity measles cases. Similarly, GMC of measles IgM was significantly lower (33.73 U/mL) in high avidity cases than in low avidity cases (166.07 U/mL) (t = −6.99, P < 0.001). Positive IgM rate and GMC remained lower in high avidity cases several days after rash onset (Figure 1).
Measles Virus IgG Avidity Assay for Use in Identification of Measles Vaccine Failures in Tianjin, China
doi: 10.3967/bes2019.102
- Received Date: 2019-03-31
- Accepted Date: 2019-08-16
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Key words:
- Measles /
- IgG avidity /
- China /
- Primary vaccine failures /
- Secondary vaccine failures
Abstract:
Citation: | DING Ya Xing, MAO Nai Ying, ZHANG Yan, LEI Yue, GAO Zhi Gang, XU Wen Bo, ZHANG Ying. Measles Virus IgG Avidity Assay for Use in Identification of Measles Vaccine Failures in Tianjin, China[J]. Biomedical and Environmental Sciences, 2019, 32(11): 804-811. doi: 10.3967/bes2019.102 |