Table 2. Patient characteristics and laboratory results for patients with laboratory-confirmed measles during the outbreak in the Gothenburg area, Sweden, December 2017–January 2018 (n = 28).
| Patient | Infection typea | IgM acute sera |
IgG (mIU/mL) acute sera |
IgM FU |
IgG (mIU/mL) FU |
Ct value NP | Ct value urine | Ct value blood | Avidity indexb (%) acute sera |
Avidity indexb (%) FU |
|---|---|---|---|---|---|---|---|---|---|---|
| 1 | N | Equivocal | Neg | Pos | 6,191 | 18 | 21 | Neg | NA | 54 (E) |
| 2 | N | Pos | Neg | Pos | 10,083 | 22 | 22 | 38 | NAc | 67 (HA) |
| 3 | N | Pos | Neg | ND | ND | 17 | 20 | 17 | NA | ND |
| 4 | N | Neg | Neg | ND | ND | 28 | ND | 36 | NA | ND |
| 5 | N | Pos | Neg | ND | ND | 22 | 26 | 31 | NA | ND |
| 6 | N | Equivocal | Neg | ND | ND | 20 | 24 | 31 | NA | ND |
| 7 | N | Pos | Neg | Equivocal | 13,454 | 18 | ND | ND | NAc | 73 (HA) |
| 8 | N | Pos | Neg | ND | ND | 19 | 17 | 32 | NA | ND |
| 9 | N | Neg | Neg | Neg | 3,648 | 22 | ND | ND | NA | 44 (E) |
| 10 | N | Pos | Neg | Equivocal | 9,420 | 17 | ND | ND | NA | 58 (E) |
| 11 | N | Pos | Neg | Pos | 12,682 | 18 | 22 | 32 | NA | ND |
| 12d | N | Neg | 579 | Neg | 5,204 | 19 | 19 | 32 | 16 (LA) | 45 (E) |
| 13 | B | Neg | 11,952 | Neg | 29,730 | 33 | 33 | Neg | > 99 (HA) | > 99 (HA) |
| 14 | B | Equivocal | 22,650 | Equivocal | > 30,000 | 35 | 38 | Neg | 94 (HA) | 91 (HA) |
| 15 | B | Neg | 7,040 | Neg | > 30,000 | 25 | 35 | Neg | 80 (HA) | 89 (HA) |
| 16 | B | Neg | 508 | Equivocal | 26,891 | 32 | 31 | Neg | 65 (HA) | 96 (HA) |
| 17 | B | Neg | 2,513 | Neg | > 30,000 | 34 | 34 | ND | 78 (HA) | 92 (HA) |
| 18 | B | Equivocal | 5,593 | ND | ND | 24 | 27 | Neg | NDe | ND |
| 19 | B | Neg | 27,960 | Neg | > 30,000 | 31 | 29 | Neg | 99 (HA) | > 99 (HA) |
| 20 | B | Equivocal | 29,425 | Neg | 28,030 | Neg | 35 | Neg | 96 (HA) | 97 (HA) |
| 21 | B | Neg | 3,931 | Neg | > 30,000 | Neg | 34 | Neg | 85 (HA) | > 99 (HA) |
| 22 | B | Neg | 4,350 | Equivocal | > 30,000 | 37 | 29 | Neg | 82 (HA) | > 99 (HA) |
| 23 | B | Neg | Neg | ND | ND | 31f | ND | ND | ND | ND |
| 24 | B | Equivocal | 28,980 | Neg | > 30,000 | Neg | 34 | Neg | 90 (HA) | 97 (HA) |
| 25 | B | Neg | 2,115 | Equivocal | 27,883 | Neg | Neg | 36 | 71 HA) | 94 (HA) |
| 26 | B | Equivocal | 209,570 | Neg | > 30,000 | Neg | 34 | Neg | 94 (HA) | 98 (HA) |
| 27 | B | Equivocal | 192,190 | Neg | > 30,000 | 31 | Neg | Neg | 91 (HA) | 99 (HA) |
| 28 | B | Neg | Neg | ND | ND | 37 | 39 | 40 | NDe | ND |
B: breakthrough infection; Ct: cycle threshold; E: equivocal; FU: follow-up visit; HA: high avidity; LA: low avidity; N: naïve infection; NA: not applicable; ND: not done; Neg: negative; NP: nasopharynx; Pos: positive.
a Breakthrough infection was defined as a confirmed case of measles in an individual with history of vaccination and/or positive IgG levels (> 399 mIU/mL) in acute serum at or after onset of rash (if taken within 4 days), regardless of whether post-exposure prophylaxis was given or not.
b Relative avidity index was calculated according to instructions by the manufacturer: HA > 60%, E 40–60%, LA < 40%.
c Low levels of low-avidity IgG antibodies (below the detection limit of the standard IgG assay) were detected, in Patient 2 (31%) and in Patient 7 (23%).
d Patient 12 had no history of vaccination against measles and no history of measles infection. This patient presented low levels of IgG (579 mIU/mL) at first sampling 5 days after onset of rash and had received post-exposure measles vaccine 7 days before onset of rash.
e Not done because of insufficient material.
f Performed at a different laboratory with the same method.