Yes it is recommeded to vacinate meat birds. But if you only have a few, no history of Mareks, and no possible contamination you should be ok But here is a few quotes from Avian Pathology Journal,
.In ovo vaccination of chickens is an importanti nnovation for the poultry industry. Experimental in ovo vaccination has been used for a number of diseases including Mareks disease (MD) (Sharma & Burmester, 1982; Sharma & Graham, 1982; Sharma et al., 1984), infectious bronchitis (Wakenell& Sharma, 1986; Walkenell et al., 1995), infectious bursal disease (Sharma, 1985), Newcastle
disease (Ahmed & Sharma, 1992), coccidiosis (Ruff et al., 1988; Watkins et al., 1995) and acombination of diseases (Gagic et al., 1999; Hill &Sharma, 1999). However, to date, this technology is most widely used to vaccinate broiler chickens against MD (Ricks et al., 1999). The two main objectives of in ovo vaccination are: (1) to maximize the interval between vaccination and possible early natural challenge by virulent virus, allowing sufficient time for adequate vaccinal immunity to develop (Sharma & Burmester, 1982); and (2) to reduce handling of chicks and labour costs in the hatchery associated with post-hatch subcutaneous vaccination (Gildersleeve et al., 1993). ISSN 0307-
So I hope that
The fact that it is so widely used by meaties should indicate to you it is ok. Plus I don't think you are going to be worried about the labour cost to give the chicks injections.
Have a fun and healthy time raising the meaties.
Source: P. L. Young, et al. "Influence of vaccine deposition site on post-vaccinal viraemia and vaccine efficacy in broiler chickens following in ovo vaccination against Marek's disease." Avian Pathology 30.5 (2001): 525-533. Academic Search Complete. EBSCO. Web. 27 Apr. 2011.
I hope this helps,
Christal