*2.1. Outcome Variables*

The individual survey schedule of the LASI asked "have you ever received any immunizations for adults, such as the influenza vaccine, pneumococcal vaccine, hepatitis B vaccine, or typhoid vaccine?". Multiple answers were allowed for the above question. If the response was "yes" for a particular vaccine, then we considered an individual to be vaccinated for that particular vaccine such as influenza vaccine, pneumococcal vaccine, hepatitis B vaccine, or typhoid vaccine which formed the main outcomes of interest for our study.

### *2.2. Independent Variables*

We took into account the following socio-economic and demographic factors: age (in years), sex, residence, caste, education, occupation, marital status, MPCE quintile, and health insurance. Answers to the age-based question "how old were you on your last birthday?" were categorized into three groups, namely 60–69 years, 70–79 years, and >80 years. Sex was recorded based on observation as male or female. The residence of the respondents was divided as urban or rural. Caste was classified into four groups, namely scheduled caste, scheduled tribe, other backward class, and others (includes: no caste/tribe and none of these) based on two questions "what is your caste or tribe?" followed by "Do you belong to a scheduled caste, a scheduled tribe, other backward class, or none

of these?". Education of the respondents was assessed through the question "have you ever attended school?" with responses yes or no corresponding with formal education and no formal education, respectively. The current occupation status of the respondent grouped as currently employed or currently unemployed was based on the responses to "have you ever worked for at least 3 months during your lifetime?". Marital status was classified based on "what is your current marital status?" with responses grouped as with partners (currently married or live-in relationship) or without partners (widowed, divorced, separated, deserted, or never married). The economic status was based on the monthly per capita expenditure (MPCE) grouped into quintiles ranging from the most deprived to the most affluent class. The health insurance coverage among participants was assessed through "are you covered by health insurance?" with responses as yes or no. Based on an extensive literature search, ten self-reported most common NCDs such as hypertension, diabetes, cancer, chronic lung disease, chronic heart disease, stroke, arthritis, psychiatric problems, and high cholesterol were taken into account based on one of the questions: "has any health professional ever diagnosed you with the following chronic conditions or diseases?". Multimorbidity was defined as having two or more chronic conditions out of the above-mentioned chronic conditions.
