The COVID-19 Open Access Project (COAP) living evidence database will not longer be updated after 28th February 2022. The database up to that date will remain available for searching indefinitely. During that time we have indexed over 300,000 peer-reviewed articles and preprints on SARS-CoV-2 and COVID-19
We recommend using the World Health Organization (WHO) COVID-19 database as an alternative search engine.
We conduct a systematic search of the COVID-19 literature daily. We retrieve data from EMBASE via OVID; MEDLINE via PubMed; BioRxiv; MedRxiv; and PsychInfo. We clean the list of references and remove duplicate records. We import the new references into the central COAP database.
A systematic search of the COVID-19 literature is performed Monday to Friday. The team retrieve data from 76 different databases, including the five databases covered by COAP. You can find all searched databases here. The team remove duplicate records in EndNote and Distillr using the Bramer method. Further screening is done by expert reviewers although some duplicates may remain in the database. If you do a search in this database, you can select which databases to include in a search.
The search terms that are used for retrieving articles about SARS-CoV-2 and COVID-19 from the two databases differ. You can find a detailed explanation of the COAP search strategy here and of WHO COVID-19 database here.
In the COAP database truncation is supported without an asterisk ‘*’. Searching using a keyword will identify any words that contain the keyword. For example, symptom = asymptomatic, symptoms, pre-symptomatic, etc. Alternatively, in the WHO COVID-19 database truncation is supported with asterisk symbol ‘*’ or dollar sign ($). For example, symp* = symptom, symptoms, symptomatic, sympathetic, etc.
In COAP, Boolean operators (AND, OR, NOT) must be outside the parenthesis. You can find detailed instructions in the “Help” tab here. In the WHO COVID-19 database, Boolean operators (AND, OR, NOT) can be inside or outside the parenthesis. You can find more detailed information here.
Users may find that the databases give slightly different results. We explored how the search results differed in several example searches on 15th February 2022 (Table 1).
| Search results (n records) | |||
|---|---|---|---|
| Search Strings | COAP | WHO COVID-19 database (including only the 5 databases used in COAP) | WHO COVID-19 database (including all databases from WHO) |
| (child) and (variant) | 374 | 109 | 123 |
| (child*) and (variant) | Syntax error | 227 | 288 |
| (child) and (omicron) | 25 | 8 | 10 |
| (child*) and (omicron) | Syntax error | 22 | 27 |
| (asymptomatic) or (presymptomatic) | 10,008 | 9726 | 12,510 |
| (asymptomatic) or (pre-symptomatic) | 10,047 | 10,098 | 12,998 |
Table 1. Results of specific search strings in the COAP and the WHO COVID-19 databases on 15th February 2022
Although the following search strings are equivalent, they generate a different number of records in each database:
“(child) and (omicron)” in COAP and “(child*) and (omicron)” in WHO COVID-19 database (Table 1).
We believe that the number of records differed in the search results because of the different search strategies and the order in which the databases collect records from various sources.