Serological surveillance of healthcare workers to evaluate natural infection- and vaccine-derived immunity to SARS-CoV-2 during an outbreak in Dili, Timor-Leste

Comparative IgG responses to SARS-CoV-2 after natural infection or vaccination

“…Future research may also look at the relationships between viral variants and population-wide antibody profiles in vaccinated and unvaccinated cohorts, as well as how antibody characteristics connect to clinical outcomes and transmissibility in each group. Moreover, additional focus should be paid to hybrid immunity and the impact of repeated (or breakthrough) infections and boosters, including extended follow-up (8, 20) for antibody durability and titer beyond one year from each type of exposure in the general population. Flexible study designs that can more easily accommodate adjustments made in response to a rapidly changing viral variant landscape would help future studies maintain relevance over time as SARS-CoV-2 transitions from pandemic to endemic circulation.…”

“…Prospective evaluations tend to be limited in sample size (12,14,(20)(21)(22), have short serological monitoring periods, (9,20,22) or analyses were completed retrospectively (23,24). Many studies utilize populations of healthcare workers who may encounter infectious agents -including SARS-CoV-2 -more frequently than other members of the community, limiting generalizability of results due to potential repeated exposures and subclinical infections (9,12,20,25). Several quality studies have evaluated the effectiveness of vaccination-and/or infection-acquired immunity over time, but have lacked a serological component (24)(25)(26).…”

“…Despite a growing body of literature, availability of data directly comparing antibody responses following vaccination versus natural infection is limited. Prospective evaluations tend to be limited in sample size (12, 14, 20-22), have short serological monitoring periods,(9, 20, 22) or analyses were completed retrospectively (23, 24). Many studies utilize populations of healthcare workers who may encounter infectious agents – including SARS-CoV-2 – more frequently than other members of the community, limiting generalizability of results due to potential repeated exposures and subclinical infections (9, 12, 20, 25).…”

The COVID-19 laboratory response in Timor-Leste: a story of collaboration

“…Acquisition of anti-N antibodies were also seen in 39.5% (30/76) of HCWs signalling an infection, post first dose of vaccine. 13 The second study using residual blood was conducted in Dili and 4 regional sites of Timor-Leste between March and October 2021. During that period a total of 1652 residual serum samples were tested; prevalence of anti-spike IgG increased from 8.3% (95% CI 1.5–35.4%) to 87.0% (95% CI 77.7–92.8%) and anti-N IgG increased from 8.3% (95% CI 0.0–24.3%) to 45.5% (95% CI 34.8–56.3%).…”

Strong relationships between the Northern Territory of Australia and Timor-Leste

“…Menzies, LNS and researchers from the Ministry of Health, have collaborated with the Australian National Centre for Immunisation Research and Surveillance (NCIRS) to carry out seroprevalence studies involving healthcare workers, 7 residual serum samples from hospital laboratories, and a nationwide population-representative cohort of more than 5000 people. The research is aimed at improving understanding of the epidemiology and vaccine coverage for key vaccine-preventable diseases, including measles, rubella, COVID-19, dengue and hepatitis B.…”