survey and administrative vaccination figures. When additionally controlling for region fixed effects, the correlation between statistical performance and discrepancies in vaccination rates is no longer statistically significant with the effect absorbed by the Sub-Saharan Africa regional dummy.

We take this as evidence that discrepancies between administrative records and survey data are more likely and larger where administrative data systems are weaker and suffer from lower capacity.

# **Numerator issues (number of people currently vaccinated)**

Next, we turn our attention to the possible sources of bias in the administrative data (Table 10). We distinguish between numerator issues (misreporting of the number of people currently vaccinated) and denominator issues (under- or overestimating target population size).

On the side of potential numerator issues, we find large time gaps in reporting to be common. While the average frequency of reporting is fairly high (every 2.4 days) across our sample of 36 LMICs, gaps can get as long as close to half a year without a vaccination rate report (175 days between July 2022 and January 2023 in Ethiopia). The longest time gaps between two data points are almost two months (54.9 days) when averaging across our sample of countries, with 26 out of 36 countries (72%) having gaps of 30 days or longer. Fourteen countries (42%) have gaps longer than 2 months (60 days). Gaps are even greater in our sample of five Sub-Saharan African countries that are the subject of our survey experiments. Here, the average longest gap amounts to 3 months (90 days) with all countries displaying gaps between reports of 42 days or more.

We also find large jumps in reported coverage between data points in the administrative data. Across our sample of LMICs, as well as in our smaller sample of five Sub-Saharan African countries, we find the average increase in reported COVID-19 vaccine coverage to amount to 0.2 percentage points in between two reports (0.11pp and 0.04pp on a per-day basis, respectively). However, these small increases on average hide some larger jumps. In 16 out of 36 countries (44%), jumps of 5 percentage points or more occur in between reports and in seven countries, jumps exceed 10 percentage points. There are extreme cases, such as in Nicaragua where reported coverage jumped by 37 percentage points within a two-week window in November 2021 or Guyana that reported vaccinating 4% of its population on a single day in November 2022. Owing to the slow progress of vaccination campaigns in the region, these jumps are somewhat smaller but still substantial in our sample of Sub-Saharan African countries.

Given the at times infrequent reporting of vaccination rates and large jumps in coverage, one possibility would be that cases where survey estimates exceed administrative figures reflect lags in the administrative data. We bound these potential lags by reporting the mean number of days it takes for administrative coverage to catch up with coverage estimated from surveys wherever survey estimates exceeded administrative reports to start with among the 36 LMICs we study.<sup>20</sup> We find that these lags would have to be very substantial in order for them to explain the

> 20 As such, the analysis sample for this exercise excludes cases where survey estimates are below administrative reports and where the administrative data had not caught up to survey estimates by March 31, 2023.

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