Frontiers in Medicine (Jul 2022)

High secondary attack rate and persistence of SARS-CoV-2 antibodies in household transmission study participants, Finland 2020–2021

  • Timothée Dub,
  • Anna Solastie,
  • Lotta Hagberg,
  • Oona Liedes,
  • Hanna Nohynek,
  • Anu Haveri,
  • Camilla Virta,
  • Saimi Vara,
  • Mervi Lasander,
  • Nina Ekström,
  • Pamela Österlund,
  • Katja Lind,
  • Katja Lind,
  • Hanna Valtonen,
  • Heidi Hemmilä,
  • Heidi Hemmilä,
  • Niina Ikonen,
  • Timo Lukkarinen,
  • Arto A. Palmu,
  • Merit Melin

DOI
https://doi.org/10.3389/fmed.2022.876532
Journal volume & issue
Vol. 9

Abstract

Read online

BackgroundHousehold transmission studies offer the opportunity to assess both secondary attack rate (SAR) and persistence of SARS-CoV-2 antibodies over time.MethodsIn Spring 2020, we invited confirmed COVID-19 cases and their household members to four visits, where we collected nasopharyngeal and serum samples over 28 days after index case onset. We calculated SAR based on the presence of SARS-CoV-2 neutralizing antibodies (NAb) and assessed the persistence of NAb and IgG antibodies (Ab) against SARS-CoV-2 spike glycoprotein and nucleoprotein.ResultsSAR was 45% (39/87), including 35 symptomatic secondary cases. During the initial 28-day follow-up, 62% (80/129) of participants developed NAb. Of those that seroconverted, 90% (63/70), 85% (63/74), and 78% (45/58) still had NAb to early B-lineage SARS-CoV-2 3, 6, and 12 months after the onset of the index case. Anti-spike IgG Ab persisted in 100% (69/69), 97% (72/74), and 93% (55/59) of seroconverted participants after 3, 6, and 12 months, while anti-nucleoprotein IgG Ab levels waned faster, persisting in 99% (68/69), 78% (58/74), and 55% (39/71) of participants, respectively.ConclusionFollowing detection of a COVID-19 case in a household, other members had a high risk of becoming infected. NAb to early B-lineage SARS-CoV-2 persisted for at least a year in most cases.

Keywords