Skip to main content

Table 1 Antibody status in children with acute subtype-specific influenza primary infections and re-infections, with primary and re-infections defined according to the absence or presence of subtype-specific IgG in HI assays

From: Similar severity of influenza primary and re-infections in pre-school children requiring outpatient treatment due to febrile acute respiratory illness: prospective, multicentre surveillance study (2013–2015)

 

Children treated in outpatient practices for acute influenza A virus infection, by subtype

Acute A(H3N2) infections

Acute A(H1N1)pdm09 infections

Primary infections

Re-infections

Primary infections

Re-infections

N = 78

N = 14

N = 44

N = 4

Previous influenza infection indicated by IgG antibody status

 No influenza A IgG

62

–

25

–

 A(H3N2) IgG

–

14

19

3

  Titer

 

13 with non-protective titer (< 1:40), 1 with protective titera (1:160)

7 with non-protective titer, (< 1:40), 12 with protective titer (1:40–1:450)

1 with non-protective titer (< 1:40), 2 with protective titer (1:160–1:320)

 A(H1N1)pdm09 IgG

16

8

–

4

  Titer

2 with non-protective titer (< 1:40), 14 with protective titer (1:40 to 1:320)

4 with non-protective titer (< 1:40), 4 with protective titer (1:40–1:320)

 

3 with non-protective titer (< 1:40), 1 with protective titera (1:80)

  1. Data from a subgroup of 140 influenza A outpatients aged 1–5 years, with known influenza virus subtype of the acute infection and subtype-specific influenza A IgG antibody determination. Influenza A IgG presence indicates a previous infection with a specific influenza A subtype. Bold letters in the columns “Re-infections” indicate patients with IgG antibodies against the subtype of the acute infection, thus determining the classification as subtype-specific “re-infection”. For these patients, information in bold italic letters describes the level of protection according to the IgG antibody titer. By definition, in acute subtype-specific influenza A primary infections, there are no IgG antibodies against the specific subtype causing the disease; however; these patients may possess IgG against the other influenza A subtype
  2. For each IgG subtype, the number of patients with non-protective or normally protective titers were reported. Numbers in brackets refer to IgG antibody titers from hemagglutination inhibition assays (titer of ≥ 1:40 considered ‘protective’ against infection with the respective subtype)
  3. Note that the IgG antibody status is presented only for influenza virus A. For those children in Table 1 with detected influenza virus A titers, the titers for lineage-specific influenza virus B IgG were additionally evaluated; of these patients, 40 had also IgG against at least one influenza virus-B lineage (details not shown)
  4. aIndicates patients with current infection by a specific influenza virus A subtype despite a normally protective titer of the relevant subtype-specific IgG antibodies
Back to article page

BMC Infectious Diseases

ISSN: 1471-2334

Contact us