Preplanned Studies: COVID-19 Vaccination Rates of People Who Use Drugs — Chengdu City, Sichuan Province, China, November 2021 – February 2022

Vaccination is expected as the most effective tool for protecting people from getting seriously ill or dying of COVID-19 in the absence of specialized treatment drugs (1). By June 10, 2022, the data of the World Health Organization (WHO) reported that about 11.83 billion doses had been administered globally and an average of 65.7% of the worldwide population have received at least 1 dose of a COVID-19 vaccine (2). However, vaccination coverage was significantly uneven across populations and geographically. Previous studies have already shown that people who use drugs (PWUDs) in particular are vulnerable and easily neglected by public health infrastructure, and have lower vaccination coverage in comparison with the general population (3-8).

One reason is that, in many countries, PWUDs were not included in initial priority groups for vaccination of COVID-19. In addition, they are more likely to face barriers to vaccination on the basis of insufficient vaccine supplies (4). Third, PWUDs often possess lower vaccination acceptance rates compared to the general population (5). One study on patients with substance use disorders in the United States showed that nearly half of the patients expressed unwillingness to get a COVID-19 vaccine, even though they — particularly those with opioid use disorders — had been told they were at a higher risk of being infected and getting severally ill as a result of chronic lung or liver diseases (6). Two studies further reported that only 10% (vs. 60% of the general population) and 57% (vs. 77% of the general population) of people who inject drugs received COVID-19 vaccines during the early phase of COVID-19 in the United States and Australia, respectively (7-8).

China was one of the first countries to initiate nationwide vaccinations for COVID-19 and achieved a coverage rate of 87.85% by March 18, 2022 (9). However, it was not clear prior to this study how high COVID-19 vaccination rates might have been among PWUDs in China. As such, this study endeavored to investigate PWUD vaccination coverage rates by analyzing data from the Management and Control Database for Persons Who Use Drugs in one particular Sichuan district.

This research analyzed anonymous data in the Management and Control Database for Persons Who Use Drugs in one district of Chengdu City, Sichuan Province, China, from November 2021 to February 2022, which is part of National Dynamic Management and Control Database for Persons Who Use Drugs (10). The data included age, sex, drug categories, last treatment approaches, drug use history, drug use modes, disease history, dosage of vaccine (single dose, double doses, and three doses), time of vaccination, and self-reported reasons of non-vaccination. All the data were updated in February 2022 to reflect participants’ latest vaccination status. There were two reasons for this study to select this district in Sichuan Province in particular. One reason is that it is difficult to access the PWUD data necessary for this type of research in other districts. Second, Sichuan ranked 5th in drug users, 6th in terms of GDP, and 8th in the service industry nationally. Therefore, it has a fair degree of representativeness for PWUDs nationwide.

The PWUDs were divided into groups based on their vaccination information (i.e. presence of vaccination, type of vaccine, and time of vaccination). The vaccination rate was calculated by the number of fully vaccinated persons divided by the total of PWUDs who had clear vaccine information. The drugs that PWUDs used were divided into opioid drugs (ex. heroin), synthetic drugs (ex. methamphetamine), psychoactive substances (ex. marijuana, LSD), and polydrug use (ex. heroin and methamphetamine together) based on international classifications.

All data were double-checked by Erri Du and Pengyu Jiang. The chi-square test was used to compare the above characteristics between the two groups (vaccinated and unvaccinated); the odds ratios (ORs) and their 95% Confidence Intervals (CIs) for the multivariable binary logistic regression were used to estimate factors associated with the vaccination of PWUDs.

A two-sided P value of 0.05 or less was regarded as significant. All the data cleaning was done using Excel (version 2017, Microsoft Corp., Redmond, WA, US) and WPS Office (version 3.9.6, Kingsoft Office Corp., Beijing, China). All analysis was done using IBM SPSS (version 24.0, IBM Corp., Armonk, NY, US). The data were anonymized without participant identifiers so that this research does not require additional regulation by the Institutional Review Board.

Among a total of 1,671 available records of PWUDs in the region, 310 PWUDs did not have vaccination information, 192 PWUDs could not specify their vaccination situation by type of vaccine and/or time of vaccine, 56 PWUDs had not finished vaccination, and 1,113 PWUDs with clear vaccinating information were included in the final analysis (Figure 1). The fully vaccinated PWUDs with single dose, double doses, and triple doses were 2, 869, and 12, respectively (Figure 1).

Figure 1. 

The management of data for PWUDs

Abbreviation: PWUDs=people who use drugs.

86.79% of the PWUDs were 30–59 years old. Men accounted for 74.39% of the sampled PWUDs. About 47.80% of the PWUDs had jobs, while 36.30% PWUDs reported being unemployed (Table 1). Synthetic drugs and opioids were the main drugs used by sampled PWUDs (66.94% and 19.84%, respectively). Oral use was the most popular reported drug use mode (81.49%). About 56.06% of the PWUDs started using drugs less than 5 years ago, and 84.82% had no disease records. More than 61.54% of the PWUDs were still in treatment (Table 1).

By February 2022, 883 PWUDs were fully vaccinated, and the vaccination rate reached 79.34% among all PWUDs included in this analysis (Table 1). However, 101 of the 230 unvaccinated PWUDs had illness records, so the vaccination rate could be calculated as 87.25% if this study excluded these 101 PWUDs (Table 1). Occupation and diseases were significant risk factors related to the vaccination rate of PWUDs (Table 2, Supplementary Table S1). The finding indicated that the PWUDs unemployed and employed in service sectors were less likely to be vaccinated than those in public institutions and enterprises (the reference group), the risk of unvaccination were about 3 times [2.52 (1.33–4.77)] and 4 times [3.81 (2.03–7.14)] that of the reference group, respectively (Table 2). The PWUDs with infectious diseases, chronical diseases, or both infectious and chronical diseases were 9 times [9.49 (3.67–24.59)], 8 times [8.22 (5.19–13.03)], and 4 times [3.73 (1.12–12.41)] the risk of unvaccination compared to those who did not report any diseases, respectively (Table 2).