Numerous studies have revealed severe damage to male fertility from severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2) infection, raising concerns about the potential adverse impact on reproductive function of the coronavirus disease 2019 (COVID‐19) vaccine developed based on the virus. Interestingly, there are several researchers who have studied the impact of the COVID‐19 mRNA vaccine since then but have come up with conflicting results. As a near‐ideal candidate for mass immunization programs, inactivated SARS‐CoV‐2 vaccine has been widely used in many countries, particularly in less wealthy nations. However, little is known about its effect on male fertility. Here, we conducted a retrospective cohort study at a single large center for reproductive medicine in China between December 2021 and August 2022. Five hundred and nineteen fertile men with no history of laboratory‐confirmed COVID‐19 were included and categorized into four groups based on their vaccination status: unvaccinated group (n = 168), one‐dose vaccinated group (n = 8), fully vaccinated group (n = 183), and booster group (n = 160). All of them underwent a semen analysis and most had serum sex hormone levels tested. There were no significant differences in all semen parameters and sex hormone levels between the unvaccinated group and either vaccinated group. To account for possible vaccination‐to‐test interval‐specific changes, sub‐analyses were performed for two interval groups: ≤90 and >90 days. As expected, most of the semen parameters and sex hormone levels remained unchanged between the control and vaccinated groups. However, participants in vaccinated group (≤90 days) have decreased total sperm motility and increased follicle‐stimulating hormone level compared with the ones in unvaccinated group. Moreover, some trends similar to those found during COVID‐19 infection and recovery were observed in our study. Fortunately, all values are within the normal range. In addition, vaccinated participants reported few adverse reactions. No special medical intervention was required, and no serious adverse reactions happened. Our study suggests that inactivated SARS‐CoV‐2 vaccination does not impair male fertility, possibly due to the low frequency of adverse effects. This information reassures young male population who got this vaccine worldwide, and helps guide future vaccination efforts.

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Omicron (B.1.1.529) was first detected in a sample collected in Botswana on November 11, 2021, and has rapidly replaced Delta as the dominant global variant given the robust transmissibility. Moreover, it displays a lower virulence than other variants. However, the pathogenicity of Omicron appears to be underestimated in view of the increasing levels of herd immunity through natural infection or vaccination. Additionally, the volume of hospitalizations and deaths increase in proportion to the number of cases due to the high transmissibility of Omicron. Therefore, vaccination remains an important public health priority. Notably, a series of important mutations in the Omicron spike protein, especially in the receptor-binding domain and N-terminal domain, appears to be associated with immune escape capacity, reducing the willingness of people to receive vaccines. Herein, we provide an in-depth discussion to assess the effectiveness of the second and third vaccination against Omicron variant. On the one hand, the two-dose vaccination program adopted by many countries is insufficient to prevent Omicron infection given the mutations correlated with immune escape and the decline in vaccine efficacy over time. On the other hand, booster dose significantly increases the protective efficacy against Omicron infection. Most importantly, heterologous third dose vaccination induces a more robust immune response than homologous booster dose. Therefore, under the special background of this pandemic, there is an urgent need to accelerate the third dose of vaccination, especially providing better booster vaccination strategies, to combat emerging Omicron variant.

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The coronavirus disease 2019 , which is caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has posed a potential threat to infant health. The World Health Organization recommended that the benefits of breastfeeding far outweigh the potential risk of transmission, but there is no denying that the current evidence is insufficient. Moreover, although the COVID-19 mRNA vaccine has played an effective role in protection against infection, individuals have increasing concerns about the safety of breastfeeding after vaccination, and which have caused some breastfeeding women to postpone vaccination or stop breastfeeding early. Thus, in this review, we provide an in-depth discussion of whether SARS-CoV-2 and the vaccine will affect babies through breast milk. On one hand, only a very small number of milk samples were identified positive for viral RNA and almost impossible to be live virus particles. The milk of most lactating women after vaccination did not contain vaccine-related mRNA and polyethylene glycol. On the other hand, the antibodies and biologically active molecules like lactoferrin are abundant in the milk of lactating women who have been infected or vaccinated, which can provide potential protection against infants' respiratory and gastrointestinal infections. Therefore, in terms of implications for clinical practice, the results of our study support that lactating women who have been infected or vaccinated should be encouraged to breastfeed their infants under the premise of taking appropriate sanitary measures.