您可以使用字典来Map等价项，然后使用groupby + agg和numpy.select：

eq_vaccines = {'B': 'BC', 'C': 'BC'}

vac = df['vaccine'].map(eq_vaccines).combine_first(df['vaccine'])
applied_any = df.groupby(['patient', vac])['applied?'].transform('max').eq(1)

import numpy as np
df['status'] = np.select([df['applied?'].eq(1), applied_any],
                         ['Ok', 'Applied equivalent vaccine'], 'Missing')

输出：

patient vaccine  applied?                      status
0        1       A         1                          Ok
1        1       B         1                          Ok
2        1       C         0  Applied equivalent vaccine
3        2       A         0                     Missing
4        2       B         0  Applied equivalent vaccine
5        2       C         1                          Ok
6        3       A         1                          Ok
7        3       B         0                     Missing
8        3       C         0                     Missing

中间体表，以便于说明

patient vaccine  applied?                      status  vac  applied_any
0        1       A         1                          Ok    A            1
1        1       B         1                          Ok   BC            1
2        1       C         0  Applied equivalent vaccine   BC            1
3        2       A         0                     Missing    A            0
4        2       B         0  Applied equivalent vaccine   BC            1
5        2       C         1                          Ok   BC            1
6        3       A         1                          Ok    A            1
7        3       B         0                     Missing   BC            0
8        3       C         0                     Missing   BC            0

def function1(dd:pd.DataFrame):
    dd1=dd.iloc[1:,[3]]
    if dd1.squeeze().eq("Ok").any():
        dd.loc[dd1.query("status == 'Missing'").index,'status']='Applied-equivalent-vaccine'
    return dd['status']

df1.groupby('patient',group_keys=False).apply(function1)

输出：

0                            Ok
1                            Ok
2    Applied-equivalent-vaccine
3                       Missing
4    Applied-equivalent-vaccine
5                            Ok
6                            Ok
7                       Missing
8                       Missing