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Volume:4 Issue:8 Number:3 ISSN#:2563-559X
OE Original

OrthoEvidence. Strategies to Increase COVID-19 Vaccinations: Review of Current Evidence

Authored By: OrthoEvidence

August 16, 2021

How to Cite

OrthoEvidence. OrthoEvidence. Strategies to Increase COVID-19 Vaccinations: Review of Current Evidence. OE Original. 2021;4(8):3. Available from: https://myorthoevidence.com/Blog/Show/143


  • - The pace of COVID-19 vaccination in countries like the United States and Canada has slowed. Exploring strategies to reduce vaccine hesitancy and boost the acceptance and uptake of COVID-19 vaccination is essential and urgent.

  • - One systematic review identified 4 types of strategies addressing vaccine hesitancy, including community health training strategy, incentive-based approach, technology-based health literacy, and media engagement (Singh et al., 2020).

  • - Another systematic review found that in general, most effective interventions were those which employed multiple strategies and were tailored to specific populations to address their specific concerns (Jarrett et al., 2015).

  • - Empirical evidence on identifying effective strategies targeting COVID-19 vaccine hesitancy is very limited. More studies are urgently needed.

[COVID-19 vaccinations] are holding steady against even the Delta variant. The problem is we don’t have enough people vaccinated. Vaccination is our way through this pandemic, but we need to ramp up the numbers.

-- Dr. Thomas Frieden, former director of the United States Centers for Disease Control and Prevention (CNN)

As of August 9, 2021, about 59% and 50% of the total population of the United States (US) have received at least one dose of COVID-19 vaccines and been fully vaccinated with COVID-19  vaccines, respectively [Centers for Disease Control and Prevention (CDC)]. However, the rates of full vaccination across the country are uneven. The vaccination rates vary from over 70% in the District of Columbia to around 35% in Alabama (Johns Hopkins Coronavirus Resource Center).

In addition, the pace of COVID-19 vaccination in the US has also slowed. The administration of COVID-19 vaccines peaked in early April 2021 with over 4 million shots being given on April 8. As of August 9, the 7-day average new doses of COVID-19 vaccines was only about 0.53 million (CDC).

Not only in the US, such trends are also found in other countries such as Canada. To date, over 70% and 60% of the Canadian population have received at least one dose of COVID-19 vaccines and been fully vaccinated with COVID-19 vaccines, respectively (COVID-19 Tracker Canada). Compared to over 0.7 million new doses administered on Jun 28, fewer than 0.2 million new doses were administered recently (COVID-19 Tracker Canada). The slowing trend in getting vaccinated against COVID-19 is worrisome because it may obstruct our efforts to reach herd immunity as soon as possible in order to control the COVID-19 pandemic.

A modelling study, assuming that vaccine efficacy was satisfactory (i.e., 80%) and the protection obtained from the vaccination lasted for life, estimated that 75% to 90% of the population needed to be vaccinated “if there is to be any chance of getting herd immunity to block the continued transmission of SARS-CoV-2” (Anderson et al., 2020). The proportion of the vaccinated population needed to be higher if the duration of protection was shorter, which is very likely the case in real world conditions. Given the 75% to 90% target, we need to get more of the remaining vaccine-eligible people to be vaccinated against COVID-19 as quickly as possible.

However, it will not be an easy task due to the low COVID-19 vaccine acceptance rates around the world. A systematic review found that many countries such as Kuwait (23.6%), Jordan (28.4%), Italy (53.7%), Russia (54.9%), Poland (56.3%), US (56.9%), and France (58.9%) had the lowest COVID-19 vaccine acceptance rates (Sallam, 2021). Therefore, exploring strategies to reduce vaccine hesitancy and boost the acceptance and uptake of COVID-19 vaccination is essential and urgent. In this OE Original, we review evidence with regard to the approaches to increasing COVID-19 vaccine acceptance and uptake

Previous OE publications on COVID-19 vaccination*

Vaccine Nationalism to Vaccine Equity: Global Solidarity to Eradicate COVID-19

Evaluation of COVID-19 Vaccines: Is Hesitancy for Some Vaccines Evidence-Based?

Towards Herd Immunity: Valuation of COVID-19 Vaccines

A Single-Dose of COVID-19 Vaccine May Not Protect Us from the SARS-CoV-2 Delta Variant: An Evidence Review

COVID-19 Vaccinations: Evidence for Delaying-Second-Dose and Mix-and-Match Strategies?

COVID-19 Vaccines: Failure Is Not An Option

* Evidence regarding COVID-19 emerges rapidly. These OE Originals and Insights can only reflect the best available evidence at the time of publication.

1. Approaches to reducing vaccine hesitancy in general

In this OE Original, we mainly focused on vaccine hesitancy, as defined by MacDonald (2015) as “delay in acceptance or refusal of vaccination despite availability of vaccination services.” We did not consider here the situations in which vaccines or access to vaccines are unavailable.

People not getting vaccinated is a very complex issue and not unique to the COVID-19 vaccination. For years before the outbreak of the COVID-19 pandemic, researchers had been investigating the possible reasons in order to identify effective solutions.

In a review conducted by Smith (2017), the author proposed that there was no “one size fits all’” solution to increase vaccine acceptance and uptake because individuals with vaccine concerns are not homogeneous in terms of their belief systems toward vaccines. A number of studies have examined the beliefs of people with concerns over vaccination (e.g., Hagood et al., 2013; Leask et al., 2012). For instance, Hagood et al. (2013) proposed a framework and classified individuals who are less likely to get vaccinated into 3 categories: vaccine rejector, vaccine resistant individuals, and vaccine hesitant individuals. The definitions of these 3 classifications are presented in Table 1.

Table 1: Definitions of three types of vaccine hesitancy given by Hagood et al. (2013)*



Vaccine Rejector

Individuals who are unyieldingly entrenched in their refusal to consider vaccine information. Vaccine rejectors are prone to beliefs that vaccines cause more harm than good, or that vaccines are a plot of a conspiracy involving governments, health organizations, and pharmaceutical companies, or other conspiracy beliefs. Vaccine rejectors are very unlikely to change their opinions on vaccines.

Vaccine Resistant Individuals

Individuals who may currently reject vaccination but are still willing to consider information regarding the efficacy and safety of vaccines, and their distrust of medical science is less likely to be tied up with beliefs in other conspiracy theories than that of vaccine rejectors.

Vaccine Hesitant Individuals

Individuals who have concerns about vaccinations but are not committed to vaccine refusal. They tend to come to the health care provider’s office with more of a generalized anxiety about vaccines. The difference between vaccine resistant and vaccine hesitant is that vaccine resistant may also hold a belief that vaccines are causing widespread damage or vaccine injuries. Vaccine hesitant individuals are considered to be the most amenable to interventions.

* To ensure accuracy, most parts of the definitions were quotes from Hagood et al. (2013).

Most strategies target vaccine hesitant individuals because “they typically are not solidly anti-vaccine and may be considered ‘fence-sitters’ on many vaccine issues, who have not strongly committed to either a ‘pro’ or ‘anti’ vaccine stance” (Smith, 2017).

A systematic review conducted by Singh et al. (2020) identified 4 types of strategies addressing vaccine hesitancy, including I) community health training strategy; II) incentive-based approach; III) technology-based health literacy, and IV) media engagement.

  1. Community health training strategy refers to the approach in which health workers or community workers address individuals’ hesitancy by targeting their lack of knowledge, misconceptions, etc. This strategy was commonly used in vaccines such as diphtheria pertussis tetanus vaccine, Bacillus Calmette-Guerin (BCG) vaccine, poliovirus vaccine, measles vaccine, influenza vaccine, and human papillomavirus (HPV) vaccine.

  1. Incentive-based approach involves monetary incentives and non-financial incentives, commonly seen in rural and lower socio-economic areas. The rationale behind this approach is to target individuals’ financial burden. Incentive-based approach has been used in vaccines including influenza vaccine, BCG, poliovirus vaccine, diphtheria pertussis tetanus vaccine, measles vaccine, hepatitis B (HBV) vaccine, etc.

  1. Technology-based health literacy involves informative posters, leaflets, videotapes, social media, organizing lectures to address issues of inadequate information/rumors, concerns about vaccine safety, or lack of awareness among vaccine hesitancy individuals. This approach was used in vaccines such as poliovirus vaccine, pertussis vaccine, varicella vaccine, influenza vaccine, HBV vaccine, and measles mumps rubella (MMR).

  1. Media engagement includes interventions such as reminder calls, text messages, and emails for vaccine hesitant individuals to target their negative attitude towards immunization, lack of knowledge, etc. This strategy was used in vaccines such as meningococcal (MCV4) vaccine, Tetanus diphtheria-acellular pertussis (Tdap), MMR, and influenza vaccines.

Another systematic review qualitatively summarized the effectiveness of interventions targeting vaccine hesitant individuals, which are presented in Table 2 (Jarrett et al., 2015). In general, most effective interventions were those which employed multiple strategies and were tailored to specific populations to address their specific concerns.

Table 2: Interventions that are considered successful or less successful from Jarrett et al. (2015)



Successful strategies targeting vaccine hesitant individuals (uptake increase > 25%)

Intervention that

1) directly targets unvaccinated or under-vaccinated population, or;

2) aims to increase vaccination knowledge and raise awareness, or;

3) improves convenience and access to vaccination, or:

4) targets specific populations, such as health care workers, or;

5) engages religious or other influential leaders to promote vaccination, or;

5) mandates vaccination

Less successful strategies targeting vaccine hesitant individuals (uptake increase < 10%)

Intervention that

1) improves data collection and monitoring, or;

2) extends clinic hours, or;

3) uses posters, websites, incentive-based methods, or reminder-recall methods.

2. Increasing-vaccine-uptake approaches used during the COVID-19 pandemic

Currently, most studies addressing interventions on COVID-19 vaccine hesitancy are still non-empirical research. Empirical evidence with respect to testing strategies targeting COVID-19 vaccine hesitancy is limited, and we were only able to identify 3 empirical studies, both of which investigated the use of media engagement to boost vaccination intention or uptake (Ashworth et al., 2021; Dai et al., 2021; Walkey et al., 2021). Major findings are presented in Table 3.

Media engagement approaches, including text-based reminders and information messages emphasizing private benefits or social benefits economic benefits, seemed to increase the intention to vaccinate against COVID-19 or actual vaccine uptake (Ashworth et al., 2021; Dai et al., 2021). The lottery-based approach, on the contrary, did not boost vaccination uptake in Ohio, US (Walkey et al., 2021).

Table 3: Empirical evidence regarding interventions on COVID-19 vaccine hesitancy




Text-based reminders

Media engagement

1) Two sequential RCTs delivered text-based reminders to patients one day and eight days after they received notification of vaccine eligibility. The first reminder boosted appointments and vaccination rates by 6.07 and 3.57 percentage points, respectively; the second reminder increased those outcomes by 1.65 and 1.06 percentage points, respectively. (Dai et al., 2021)

Information messages

Media engagement

1) Intentions to vaccination among participants exposed to messages that emphasized private benefits or messages emphasizing social benefits and economic benefits were 16 percentage points and 9 percentage points higher than the intentions in the control group, respectively. (Ashworth et al., 2021)

Lottery-Based Incentive

Incentive -based approach

1) The study assessed changes in COVID-19 vaccination rates before and after the Ohio vaccine lottery announcement compared with US national rates to control for the expansion of vaccine indications to adolescents. The study found no evidence to support the association between lottery-based incentive and increased vaccination rate. (Walkey et al., 2021)

RCT: randomized controlled trial; US: United States; CI: confidence interval

Apparently, more empirical studies determining the effectiveness of interventions on COVID-19 vaccine hesitancy is urgently needed. Some studies investigating the determinants of COVID-19 vaccine hesitancy may shed light on the design and testing of interventions on reducing vaccine hesitancy. For example, Soares et al. (2021) identifies several factors which were associated with vaccine hesitancy, such as young age, loss of income due to pandemic, low confidence in the COVID-19 vaccine and the health service response during the pandemic, worse perception of government measures, perception of the information provided as inconsistent and contradictory, etc.

Closing Remark

To have the COVID-19 pandemic eventually under control, it is of great importance that we develop effective strategies to reduce COVID-19 vaccine hesitancy and increase vaccine uptake. However, current empirical evidence is very limited, and therefore urgently required. To design such interventions, evidence regarding determinants of COVID-19 vaccine hesitancy might be helpful. Moreover, evidence, experiences, and principles gained from other vaccination campaigns prior to the COVID-19 pandemic may still apply. Lastly, as pointed out by Trogen et al. (2021), addressing COVID-19 vaccine hesitancy will “require a multipronged approach … There is no one-size-fits-all solution; to succeed, we must target interventions by focusing on the needs and concerns of individuals, families, and communities.


Anderson, R. M., et al. (2020). Challenges in creating herd immunity to SARS-CoV-2 infection by mass vaccination. Lancet (London, England), 396(10263), 1614-1616. doi:10.1016/S0140-6736(20)32318-7

Ashworth, M., et al. (2021). Emphasize personal health benefits to boost COVID-19 vaccination rates. Proceedings of the National Academy of Sciences, 118(32), e2108225118. doi:10.1073/pnas.2108225118

Dai, H., et al. (2021). Behavioral Nudges Increase COVID-19 Vaccinations. Nature. doi:10.1038/s41586-021-03843-2

Hagood, E. A., et al. (2013). Addressing heterogeneous parental concerns about vaccination with a multiple-source model: a parent and educator perspective. Human vaccines & immunotherapeutics, 9(8), 1790-1794. doi:10.4161/hv.24888

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Soares, P., et al. (2021). Factors Associated with COVID-19 Vaccine Hesitancy. Vaccines, 9(3). doi:10.3390/vaccines9030300

Trogen, B., et al. (2021). Understanding vaccine hesitancy in COVID-19. Med (New York, N.Y.), 2(5), 498-501. doi:10.1016/j.medj.2021.04.002

Walkey, A. J., et al. (2021). Lottery-Based Incentive in Ohio and COVID-19 Vaccination Rates. JAMA. doi:10.1001/jama.2021.11048

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