ABSTRACT
Influenza activity* in the United States during the 2018-19 season (September 30, 2018-May 18, 2019) was of moderate severity (1). Nationally, influenza-like illness (ILI) activity began increasing in November, peaked during mid-February, and returned to below baseline in mid-April; the season lasted 21 weeks,§ making it the longest season in 10 years. Illness attributed to influenza A viruses predominated, with very little influenza B activity. Two waves of influenza A were notable during this extended season: influenza A(H1N1)pdm09 viruses from October 2018 to mid-February 2019 and influenza A(H3N2) viruses from February through May 2019. Compared with the 2017-18 influenza season, rates of hospitalization this season were lower for adults, but were similar for children. Although influenza activity is currently below surveillance baselines, testing for seasonal influenza viruses and monitoring for novel influenza A virus infections should continue year-round. Receiving a seasonal influenza vaccine each year remains the best way to protect against seasonal influenza and its potentially severe consequences.
Subject(s)
Influenza A Virus, H1N1 Subtype/isolation & purification , Influenza A Virus, H3N2 Subtype/isolation & purification , Influenza B virus/isolation & purification , Influenza, Human/epidemiology , Population Surveillance , Adolescent , Adult , Aged , Antiviral Agents/pharmacology , Child , Child Mortality , Child, Preschool , Cost of Illness , Drug Resistance, Viral , Hospitalization/statistics & numerical data , Humans , Infant , Infant Mortality , Infant, Newborn , Influenza A Virus, H1N1 Subtype/drug effects , Influenza A Virus, H1N1 Subtype/genetics , Influenza A Virus, H3N2 Subtype/drug effects , Influenza A Virus, H3N2 Subtype/genetics , Influenza B virus/drug effects , Influenza B virus/genetics , Influenza Vaccines/administration & dosage , Influenza Vaccines/chemistry , Influenza, Human/mortality , Influenza, Human/prevention & control , Influenza, Human/virology , Middle Aged , Outpatients/statistics & numerical data , Pneumonia/mortality , Seasons , Severity of Illness Index , United States/epidemiology , Young AdultABSTRACT
Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection elicits an antibody response that targets several viral proteins including spike (S) and nucleocapsid (N); S is the major target of neutralizing antibodies. Here, we assess levels of anti-N binding antibodies and anti-S neutralizing antibodies in unvaccinated children compared with unvaccinated older adults following infection. Specifically, we examine neutralization and anti-N binding by sera collected up to 52 weeks following SARS-CoV-2 infection in children and compare these to a cohort of adults, including older adults, most of whom had mild infections that did not require hospitalization. Neutralizing antibody titers were lower in children than adults early after infection, but by 6 months titers were similar between age groups. The neutralizing activity of the children's sera decreased modestly from one to six months; a pattern that was not significantly different from that observed in adults. However, infection of children induced much lower levels of anti-N antibodies than in adults, and levels of these anti-N antibodies decreased more rapidly in children than in adults, including older adults. These results highlight age-related differences in the antibody responses to SARS-CoV-2 proteins and, as vaccines for children are introduced, may provide comparator data for the longevity of infection-elicited and vaccination-induced neutralizing antibody responses.