4.2 | Strengths and limitations of study
Our meta-analysis has several strengths. Compared with a similar
meta-analysis19, 5 new articles were included in this
paper. Each study sample size in this meta-analysis was larger than 100
participants and with high quality so the result can be more accurate
than others with low quality and smaller sample
size44. Furthermore, we followed the recommendations
of the Cochrane Collaboration and PRISMA statement, including a priori
protocol. Comprehensive assessment of the study quality was achieved by
using GRADE approach.
As with all systematic reviews, we may have failed to identify some
studies, especially those with negative results, therefore, this may
have influenced our findings. Finally, the length of time that the early
effective protection from BCG vaccination lasts remains unanswered. The
age of participants in this review may partially explain the result of
the protective effect of BCG vaccination. In Linehan’s study, it was
shown that any benefits of BCG vaccine are likely to be
transient.45 Therefore, a large proportion of the
protection from BCG vaccination may not be attribute to a reduction in
the risk of atopy. Nonetheless, it can be confirmed that BCG vaccination
in early childhood does reduce the risk of developing asthma in early
life.