Aug 27, 2021Nico Tuason, BSc
COVID-19 post vaccination
Before the development of vaccines, humans lived with circulating measles, polio, and smallpox viruses due to a level of long-term herd immunity following natural infection. Following the introduction of vaccines, the occurrence of these diseases was reduced by >99 percent, though, with the exception of smallpox, they were never fully eradicated. The emergence of the novel, rapidly transmissible SARS-CoV-2 virus in 2019 drove an unprecedented level of collaboration between researchers and vaccine developers to tackle the outbreak, as relying on the development of herd immunity over time was judged to be of too high a risk, especially to more vulnerable members of society. Early efforts resulted in the rapid development of several vaccines, with successful mass vaccination programs ongoing worldwide. However, with the emergence of new SARS-CoV-2 variants, long-term COVID-19 surveillance methods are needed to track both immunity and emerging variants to ensure a timely response to potential new outbreaks as workplaces, school campuses, and the like begin to reopen.
Seroprevalence studies and beyond
As a high proportion (about one third) of SARS-CoV-2 infections result in no or mild symptoms, only testing symptomatic individuals isn’t a reliable way to track the incidence or spread of the virus. A variety of measures, such as seroprevalence studies to detect antibody response against the virus and surveillance testing, will be needed to get a true picture of the number of infections. Surveillance is needed to better inform public health decisions going forward, but large sample numbers and complex sample types present major challenges.
There are several commercial assays now available to measure SARS-CoV-2 exposure rates in a population for research use, including multiplex immunoassays (e.g., Bio-Plex SARS-CoV-2 Serology Assays). These are useful research tools for identifying local asymptomatic infections in people not being tested using reverse transcription PCR (RT-PCR). In the post-vaccine scenario, these assays may also be useful for population surveillance as they are specific to SARS-CoV-2 and do not cross react with other viruses circulating in the human population.
Triaging for variants of concern
The rapid emergence of several highly transmissible SARS-CoV-2 variants (including P.1, B.1.351 [Beta], B.1.617.2 [Delta], and B.1.1.7 [Alpha]) have increased rates of infection in many regions. Although currently available COVID-19 vaccines have been shown to protect against the variants already in circulation, there is no guarantee the vaccines will protect against future variants. Public health researchers are therefore looking for a quicker way to track the spread of these variants and to rapidly prioritize which samples to submit for next-generation sequencing.
While whole genome sequencing is required to definitively identify specific variants, the number of samples that can be sequenced is limited by resources, time, and capacity constraints. Genomic surveillance tools such as RT-PCR assays are therefore vital for decision making to rapidly and cost-effectively detect the specific mutations found in the spike protein of the SARS-CoV-2 virus.
Crucial COVID-19 surveillance
The new landscape for COVID-19 includes dealing with the increasing number of variants circulating in the population. Even though the SARS-CoV-2 virus is less prone to mutation than the influenza virus, its prevalence around the world has contributed to the development of different variants. COVID-19 surveillance will therefore continue to be necessary to inform public health decisions going forward. Moreover, the answer to ensuring we’re prepared for future viral outbreaks does not lie in one method but in intelligently adopting a combination of flexible antibody detection platforms for seroprevalence studies alongside quantitative RT-PCR to monitor variant sequences directly in the population.