BY-COVID - WP5 - Baseline Use Case: COVID-19 vaccine effectiveness assessment

Matching cases to controls (1:1) and assessing covariate balance after matching

A sequence of nested (daily) trials are emulated with increasing time (t1, t2, …, tn), iterating over the days in the enrollment period. At each eligible time during the enrollment period, the vaccination status of eligible individuals is assessed and every individual who has completed a primary vaccination schedule at that time (coded here as initiation of the intervention strategy when emulating a nested target trial) is matched to an individual who has not (yet) completed the primary vaccination schedule (coded here as the control strategy when emulating a nested target trial). Newly vaccinated individuals (completing a primary vaccination schedule) are eligible for inclusion in the study, even if they had previously been selected in the “no (or partial) vaccine group”. Vaccinations have been administered in the context of national public health programs, without interference/manipulation of the research subjects.

We assess the covariate balance, which is the extent to which the distribution of covariates is similar across the intervention groups.

Standardized Mean Differences

The Standardized Mean Difference (SMD) represents a standardized difference in mean between contrasted intervention groups for each covariate.

Means intervention group Means control group Standardized mean difference
distance 0.928148006 0.789544504 1.641725020
sex_cd1 0.484558242 0.513260961 -0.057432835
sex_cd2 0.515441758 0.486739039 0.057432835
age_cd10 0.091201947 0.054159419 0.128666317
age_cd11 0.086955478 0.039800876 0.167351509
age_cd12 0.083585593 0.029772686 0.194435150
age_cd13 0.074966023 0.024050861 0.193346383
age_cd14 0.063599893 0.012979068 0.207429394
age_cd15 0.059183128 0.009248486 0.211616943
age_cd16 0.050380163 0.007964973 0.193917382
age_cd17 0.036805650 0.007425178 0.156043095
age_cd18 0.050577749 0.017249445 0.152091086
age_cd2 0.020264067 0.232495652 -1.506233112
age_cd3 0.044211319 0.145120854 -0.490890385
age_cd4 0.047989477 0.074095844 -0.122138493
age_cd5 0.042775816 0.074467702 -0.156618157
age_cd6 0.045861875 0.073640017 -0.132791923
age_cd7 0.052082026 0.068937804 -0.075861162
age_cd8 0.064574725 0.065902957 -0.005404281
age_cd9 0.084985072 0.062688178 0.079957452
residence_area_cdES241 0.164283804 0.175589276 -0.030511385
residence_area_cdES242 0.098212444 0.094584058 0.012192087
residence_area_cdES243 0.737503753 0.729826666 0.017448286
pregnancy_blTRUE 0.021848033 0.032651592 -0.073902226
essential_worker_blTRUE 0.005572809 0.006081689 -0.006835831
institutionalized_blTRUE 0.007372920 0.005565885 0.021122908
foreign_blTRUE 0.127948649 0.222407485 -0.282783266
comorbidities_blTRUE 0.374038677 0.147543933 0.468086506
immunestatus_blTRUE 0.025942765 0.010567984 0.096718282
Means intervention group Means control group Standardized mean difference
distance 0.5000002507 0.4999997493 1.412596e-03
sex_cd1 0.4776022939 0.4778632020 -5.223406e-04
sex_cd2 0.5223977061 0.5221367980 5.223406e-04
age_cd10 0.1057949421 0.1058465940 -1.679326e-04
age_cd11 0.1019515135 0.1020084630 -1.882102e-04
age_cd12 0.0986616869 0.0987014191 -1.332369e-04
age_cd13 0.0874439610 0.0874360146 2.813053e-05
age_cd14 0.0753388826 0.0753229897 6.021460e-05
age_cd15 0.0711338909 0.0711312421 1.030473e-05
age_cd16 0.0606604817 0.0606512108 3.883785e-05
age_cd17 0.0442974353 0.0442722716 1.222994e-04
age_cd18 0.0607730563 0.0607584878 6.097802e-05
age_cd3 0.0004211614 0.0004211614 0.000000e+00
age_cd4 0.0216063730 0.0216050486 9.109062e-06
age_cd5 0.0276310997 0.0276231533 4.847949e-05
age_cd6 0.0325936521 0.0325923277 7.458482e-06
age_cd7 0.0485302395 0.0485103734 9.245043e-05
age_cd8 0.0671619948 0.0671513996 4.232983e-05
age_cd9 0.0959996292 0.0959678434 1.078980e-04
residence_area_cdES241 0.1648343498 0.1648952725 -1.641985e-04
residence_area_cdES242 0.0982458232 0.0982352279 3.559674e-05
residence_area_cdES243 0.7369198270 0.7368694996 1.143012e-04
pregnancy_blTRUE 0.0177404295 0.0176636139 5.819078e-04
essential_worker_blTRUE 0.0066101145 0.0065664091 5.393504e-04
institutionalized_blTRUE 0.0088218739 0.0087265166 1.019759e-03
foreign_blTRUE 0.1079709425 0.1079325347 1.237589e-04
comorbidities_blTRUE 0.4319844250 0.4319725053 2.406300e-05
immunestatus_blTRUE 0.0299713266 0.0299594069 6.990668e-05

Propensity score distribution